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抽采钻孔孔周煤体渗流阻力分布特征试验研究

采矿与安全工程学报 2024年第3期41卷 645-654页

作者：张天军武晋宇庞明坤张磊孟钰凯刘荣涛西安科技大学安全科学与工程学院陕西西安710054 西安科技大学能源学院陕西西安710054

瓦斯抽采钻孔孔周煤体的孔隙结构变化是影响其渗流阻力的重要因素之一。为研究钻孔孔周粉碎区和裂隙区煤体渗流阻力的演化特征,采用稳态渗流法,研究了三轴压实状态下初始孔径大小对破碎煤样内部孔隙压力的影响规律,并对渗透过程中试样... 详细信息

瓦斯抽采钻孔孔周煤体的孔隙结构变化是影响其渗流阻力的重要因素之一。为研究钻孔孔周粉碎区和裂隙区煤体渗流阻力的演化特征,采用稳态渗流法,研究了三轴压实状态下初始孔径大小对破碎煤样内部孔隙压力的影响规律,并对渗透过程中试样分层界面对孔隙结构属性参数的影响进行了分析。结果表明:单一孔径试样在同一渗流速度下,随着孔径的增加,渗透状态逐渐由层流过渡到紊流,渗流阻力由黏滞阻力为主发展成惯性阻力为主,双重孔径组合试样最小孔径大小是影响孔压梯度变化的先决条件;双重孔径组合煤体平均颗粒粒径介于0.1~1.025 mm,孔喉比分布在2~4,且渗透压降随孔喉比的增加呈二次曲线规律增长;孔径大小的变化对渗透率的影响较大,随着初始孔径的增大,其影响瓦斯通过煤体的能力增强;单一孔径试样与双重孔径组合试样非达西流因子分别与粒径的倒数和粒径差的倒数呈线性关系,且随着非达西流因子的增加,非达西渗流效应越来越明显,说明非达西流β因子增长趋势受孔径大小的影响,且孔径大小突增导致流体与渗透骨架的相对接触面积减小,非达西流β因子进一步增加;可见,在瓦斯运移过程中,钻孔孔周煤体的破碎程度与煤层渗透性具有良好的一致性,结合渗透率与非达西影响因子,可以对试样孔隙几何结构参数作出定量描述,从而揭示孔隙结构变化对渗流阻力的影响。

关键词：抽采钻孔瓦斯渗流破碎煤岩渗流阻力界面改变

加载速率影响下含雁行裂纹-钻孔煤体变形破坏特征研究

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岩石力学与工程学报 2024年第3期43卷 573-586页

作者：潘红宇冯高远纪翔李佳航季冰张天军西安科技大学安全科学与工程学院陕西西安710054

为研究加载速率影响下瓦斯抽采钻孔孔周煤体变形破坏特征,开展不同加载速率下含雁行裂纹-钻孔复合缺陷煤样单轴压缩试验,结合数字图像相关技术,分析不同加载速率下复合缺陷煤样的力学特性、破坏模式与表面变形场演化规律。通过计算机视... 详细信息

为研究加载速率影响下瓦斯抽采钻孔孔周煤体变形破坏特征,开展不同加载速率下含雁行裂纹-钻孔复合缺陷煤样单轴压缩试验,结合数字图像相关技术,分析不同加载速率下复合缺陷煤样的力学特性、破坏模式与表面变形场演化规律。通过计算机视觉技术,进一步研究加载速率影响下钻孔破坏和雁行裂纹扩展特征,揭示含复合缺陷煤样变形破坏的加载速率效应。结果表明:(1)雁行裂隙-钻孔复合缺陷试样在不同加载速率作用时表现出低加载速率下高强度、高加载速率下低强度的特性,0.2 mm/min为试样的临界加载速率,在临界加载速率处试样的峰值应力、峰值应变、弹性模量的变化趋势发生改变。(2)不同加载速率下试样均呈现渐进性破坏特征,破坏形式以张拉剪切混合破坏为主,随着加载速率增加拉伸作用逐渐占到主导地位。在雁行裂隙诱导下,低加载速率时表现为沿着新生裂隙与雁行裂隙形成贯通面发生剪切错动破坏,高加载速率时表现为沿着新生裂隙水平张开发生拉伸破坏。(3)引入钻孔张缩量C来定量表征钻孔变形程度。在低加载速率下钻孔张开,C>1,随加载速率增加C逐渐降低,在高加载速率下钻孔先张开然后迅速塌缩,最终C<1。(4)雁行裂隙在加载作用下发生逆时针方向错动与张开,变形主要集中在不稳定裂隙扩展阶段。随着加载速率的增加,雁行裂隙错动量与张开量均显著增加,且试样受张拉效应增强,张开变形比例逐渐高于错动变形比例。

关键词：岩石力学加载速率抽采钻孔雁行裂纹钻孔变形裂隙扩展

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荧光共振能量转移光微流激光偏振特性分析

激光与光电子学进展 2024年第9期61卷 322-328页

作者：赵佳奇张婷婷张天俊王文杰刘绍鼎太原理工大学新型传感器与智能控制教育部重点实验室山西太原030024

将一对可以产生荧光共振能量转移(FRET)的荧光分子分别作为供体染料和受体染料,以法布里-珀罗(F-P)微腔作为光学谐振腔,基于DNA分子的G-四链体结构研究FRET光微流激光的偏振特性。实验上,研究了5种不同K+浓度的DNA(其分子两端分别标记... 详细信息

将一对可以产生荧光共振能量转移(FRET)的荧光分子分别作为供体染料和受体染料,以法布里-珀罗(F-P)微腔作为光学谐振腔,基于DNA分子的G-四链体结构研究FRET光微流激光的偏振特性。实验上,研究了5种不同K+浓度的DNA(其分子两端分别标记了一对可以产生FRET的荧光染料)溶液,用线偏振的泵浦光对其进行激发,将受体在平行偏振方向(平行于泵浦光偏振方向)的激光阈值曲线斜率和垂直偏振方向(垂直于泵浦光偏振方向)的激光阈值曲线的斜率的比值作为受体激光偏振度的检测信号。实验结果表明,随着DNA溶液中K+浓度的增加,受体激光的泵浦阈值逐渐降低,能量转换效率逐渐增加,而受体激光的斜率比逐渐变小,即偏振度逐渐降低。

关键词：荧光共振能量转移光微流激光法布里-珀罗微腔激光偏振

Tailoring Porosity and Titanium Species of TS-1 Zeolites via Organic Base-assisted Sequential Post-treatment

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Chemical Research in Chinese Universities 2022年第1期38卷 50-57页

作者： XU Wenjing LI Li zhang tianjun YU Jihong State Key Laboratory of Inorganic Synthesis&Preparative Chemistry Jilin UniversityChangchun 130012P.R.China International Center of Future Science Jilin UniversityChangchun 130012P.R.China

The exploration of high-efficient catalysts based on hierarchical Ti-containing zeolites with optimized active titanium species distribution is of great value in enhancing the epoxidation of bulky olefins. Herein, hierarchical TS-1(MFI) zeolite with an extra-large external surface area(210 m2/g) and highly active octahedral- coordinated Ti species was prepared via organic base-assisted sequential post-treatment. Such a catalyst afforded a high turnover number value(TON, 114) in 1-octene epoxidation reaction, which was over twice than that(53) of the untreated conventional microporous TS-1 parent. According to the detailed characterization results, we revealed the hierarchical porosity construction effect of tetrapropylamonium hydroxide(TPAOH) treatment(first step) and the octahedral-coordinated Ti species fabrication effect of ethylamine(EA) treatment(second step) under hydrothermal condition. Such a facile post-treatment strategy reported in this work may provide guidance for the rational synthesis of TS-1 zeolite with enhanced catalytic activity.

关键词： Post-treatment Hierarchical zeolite TS-1 Ti species Epoxidation

Zeolite-encaged Ultrasmall Pt-Zn Species with Trace Amount of Pt for Efficient Propane Dehydrogenation

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Chemical Research in Chinese Universities 2023年第6期39卷 870-876页

作者： QU Ziqiang zhang tianjun YIN Xichen zhang Junyi XIONG Xiaoyun SUN Qiming Innovation Center for Chemical Science College of ChemistryChemical Engineering and Materials ScienceJiangsu Key Laboratory of Advanced Negative Carbon TechnologiesSoochow UniversitySuzhou 215123P.R.China College of Chemistry and Materials Science Hebei UniversityBaoding 071002P.R.China PetroChina Lanzhou Petrochemical Company Lanzhou 730000P.R.China Lanzhou Petrochemical Research Center Petrochemical Research InstitutePetroChinaLanzhou 730000P.R.China

Propane dehydrogenation(PDH)has become a globe-welcoming technology to meet the massive demand for propylene,but the most commonly used Pt-based catalysts suffer from quick sintering,poor selectivity for propylene,and unsatisfied Pt ***,a series of Silicalite-1(S-1)zeolite-encaged ultrasmall Pt-Zn clusters with a trace amount of Pt[40—180 ppm(parts per million)]were developed by using a one-pot ligand-protected direct H_(2) reduction ***,the extremely low amount of Pt can significantly promote the activity of zeolite-encaged Zn catalysts in PDH *** to the high Pt dispersion,the synergy between Pt and Zn species,and the confinement effect of zeolites,the optimized PtZn@S-1 catalyst with 180 ppm Pt and 1.88%(mass fraction)Zn,exhibited an extraordinarily high propane conversion(33.9%)and propylene selectivity(99.5%)at 550℃with a weight hourly space velocity(WHSV)of 8 h^(-1),affording an extremely high propylene formation rate of 340.7 mol_(C_(3)H_(6))·g_(Pt^(-1))·h^(-1).This work provides a reference for the preparation of zeolite-encaged metal catalysts with high activity and noble metal utilization in PDH reactions.

关键词： Propane dehydrogenation Zeolite Confinement effect Bimetallic catalyst Pt-Zn

Assessing the Performance of CMIP6 Models in Simulating Droughts across Global Drylands

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Advances in Atmospheric Sciences 2024年第2期41卷 193-208页

作者： Xiaojing YU Lixia zhang tianjun ZHOU Jianghua ZHENG LASG Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science&TechnologyNanjing 210044China University of Chinese Academy of Sciences Beijing 100049China College of Geography&Remote Sensing Sciences Xinjiang UniversityUrumqi 830046China

Both the attribution of historical change and future projections of droughts rely heavily on climate modeling. However,reasonable drought simulations have remained a challenge, and the related performances of the current state-of-the-art Coupled Model Intercomparison Project phase 6(CMIP6) models remain unknown. Here, both the strengths and weaknesses of CMIP6 models in simulating droughts and corresponding hydrothermal conditions in drylands are *** the general patterns of simulated meteorological elements in drylands resemble the observations, the annual precipitation is overestimated by ~33%(with a model spread of 2.3%–77.2%), along with an underestimation of potential evapotranspiration(PET) by ~32%(17.5%–47.2%). The water deficit condition, measured by the difference between precipitation and PET, is 50%(29.1%–71.7%) weaker than observations. The CMIP6 models show weaknesses in capturing the climate mean drought characteristics in drylands, particularly with the occurrence and duration largely underestimated in the hyperarid Afro-Asian areas. Nonetheless, the drought-associated meteorological anomalies, including reduced precipitation, warmer temperatures, higher evaporative demand, and increased water deficit conditions, are reasonably reproduced. The simulated magnitude of precipitation(water deficit) associated with dryland droughts is overestimated by 28%(24%) compared to observations. The observed increasing trends in drought fractional area,occurrence, and corresponding meteorological anomalies during 1980–2014 are reasonably reproduced. Still, the increase in drought characteristics, associated precipitation and water deficit are obviously underestimated after the late 1990s,especially for mild and moderate droughts, indicative of a weaker response of dryland drought changes to global warming in CMIP6 models. Our results suggest that it is imperative to employ bias correction approaches in drought-related studies over drylands by using CMIP6 o

关键词： droughts hydrothermal conditions drylands CMIP6 model evaluation

Unraveling templated-regulated distribution of isolated SiO4 tetrahedra in silicoaluminophosphate zeolites with high-throughput computations

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National Science Review 2022年第9期9卷 19-27页

作者： Yan Li Chao Shi Lin Li Guoju Yang Junyan Li Jun Xu Qinfen Gu Xingxing Wang Ji Han tianjun zhang Yi Li Jihong Yu State Key Laboratory of Inorganic Synthesis and Preparative Chemistry Jilin University School of Textile and Clothing Yancheng Institute of Technology State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics National Center for Magnetic Resonance in Wuhan Wuhan Institute of Physics and MathematicsInnovation Academy for Precision Measurement Science and TechnologyChinese Academy of Sciences Australian Synchrotron International Center of Future Science Jilin University

Silicoaluminophosphate(SAPO) zeolites are well-known catalytic materials because of the mild acidity originating from the isolated SiO4tetrahedra in their frameworks. Regulating the distribution of isolated SiO4tetrahedra in SAPO zeolites is formidably challenging because SiO4tetrahedra tend to agglomerate to form Si islands and the isolated SiO4tetrahedra are difficult to determine using conventional characterization techniques. Here we synthesized Si-island-free SAPO-35 zeolites by using N-methylpiperidine as a new template, which exhibited excellent thermal stability compared to conventional SAPO-35 zeolites and a substantially improved methanol-to-olefins catalytic lifetime even comparable to that of commercial SAPO-34 zeolites. More strikingly, with the aid of high-throughput computations on 44 697 structure models combined with various state-of-the-art characterization techniques, for the first time, we reveal that the host–guest interactions between template molecules and SAPO frameworks determine the specific distributions of isolated SiO4tetrahedra, which are responsible for the improvement in the chemical properties of zeolites. Our work provides an insight into the template-based regulation of isolated SiO4tetrahedra in SAPO zeolites, which opens a new avenue in the discovery of promising zeolite catalysts with optimal Si O4distribution.

关键词： acidity computational chemistry heterogeneous catalysis structure–activity relationships zeolites

Catastrophic mechanism of coal and gas outbursts and their prevention and control

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Mining Science and Technology 2010年第2期20卷 209-214页

作者： LI, Shugang zhang, tianjun college of energy xi'an university of science and technologyxi'an 710054china college of science xi'an university of science and technologyxi'an 710054china

Based on the engineering observations of coal and gas outbursts during mining processes and the experimental results,we built a thin plate mechanical model for layered and spalled coal *** studied the mechanical mechanism of outbursts,due to instability,of thin plates of coal rocks under the action of in-plane load and normal load,by using the catastrophe *** total potential function is derived for the layered rock system,the cusp catastrophe model for the system is established,the bifurcation set that makes the system unstable is given,the process in which gradual change of action forces leads to catastrophic change of state is analyzed,and the effect of movement path of point(P,q) in the control space on the stability of rock plate is *** study results show that during the process of coal mining,the stability of the layered coal bodies depends not only on its physical properties and dimensions but also on the magnitudes and changing paths of the in-plane load and the normal *** the gas in the coal bodies ahead of the mining face is pre-drained,the gas pressure can be reduced and the normal load q can be ***,disasters such as coal and gas outbursts can be effectively prevented.

关键词： coal and gas outbursts catastrophe theory instability

Selective oxygen electroreduction to hydrogen peroxide in acidic media:The superiority of single-atom catalysts

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Nano Research 2024年第6期17卷 4668-4681页

作者： Ergui Luo Tongtong Yang Jingyi Liang Yuhong Chang Junming zhang tianjun Hu Junjie Ge Jianfeng Jia Key Laboratory of Magnetic Molecules and Magnetic Information Materials of Ministry of Education School of Chemistry and Materials ScienceShanxi Normal UniversityTaiyuan 030032China School of Chemistry and Materials Science University of Science and Technology of ChinaHefei 230026China State Key Laboratory of Electroanalytic Chemistry Jilin Province Key Laboratory of Low Carbon Chemistry PowerChangchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China

Two-electron oxygen reduction reaction(2e-ORR)provides an environmentally friendly direction for the on-site production of hydrogen peroxide(H_(2)O_(2)).Central to this technology is the exploitation of efficient,economical,and safe 2e-ORR *** overview starts with the fundamental chemistry of ORR to highlight the decisive role of adsorbing intermediates on the reaction pathway and activity,followed by a comprehensive survey of the tuning strategies to favor 2e-ORR on traditional precious *** latest achievements in designing efficient and selective precious-metal-based single-atom catalysts(SACs)and metal-nitrogen-carbon(M-Nx/C)catalysts,from the aspects of material synthesis,theoretical calculations,and mass transport promotion,are systematically *** introductions on the evaluation metrics for 2e-ORR catalysts and the primary reactor designs for cathodic H_(2)O_(2)synthesis are also *** conclude this review with an outlook on the challenges and direction of efforts to advance electrocatalytic 2e-ORR into realistic H_(2)O_(2)production.

关键词： oxygen reduction reaction H_(2)O_(2)production single-atom catalysts selectivity