Squeezing rock conditions at an igneous contact zone in the Taloun tunnels, Tehran-Shomal freeway, Iran: a case study

Squeezing rock conditions at the contact zone of an andesitic-basaltic body and tuff country rocks in the Taloun tunnels were investigated and analyzed. Evaluation of the rock mass properties illustrates the fact that they were significantly reduced at the contact zone, especially when wet. Detailed monitoring and measurements of tunnel-wall convergence at the contact zone in the Taloun service tunnel, during the 10 months following excavation and installation of initial support, prior to installation of heavy support, showed greater than 3% of the normalized tunnel closure. This confirms moderate squeezing conditions at the contact zone. The measured displacement was even higher than that of the fault zone in which deformation was decreased during the first month and eventually stabilized. Similarly, numerical modeling of the deformation at the contact zone not only confirmed a higher value of the tunnel convergence but also demonstrated the reduction of in situ stress and development of plastic zones across the contact zone. These data are also believed to account for the squeezing condition at the contact zone. It is expected that this condition will be significantly increased in the main road tunnels due to the fact that these tunnels are twice as wide as the service tunnel. Therefore, proper and timely support must be applied. Numerical analysis of the support at the contact zone showed that the stress due to bending moment is greater than that of the axial forces on the lining. This calls for certain support measures in the form of permanent lining and two layers of steel bars to compensate for the tensile stress exertion on the lining.     

基于全自动全站仪的地铁隧道自动化变形监测系统的设计与实现

分析了运营期间的地铁隧道结构变形采用自动化监测必要性,针对地铁隧道结构变形监测的需求,设计并实现了能够对多项目多任务进行统一控制、管理的自动化变形监测系统,详细介绍了该系统的总体构架,数据库、数据通讯、数据采集模块以及数据处理、报表输出模块的设计与实现,文章最后结合广州地铁某变形监测项目验证了该系统用来进行隧道监测的实用性和稳定性。     

超高效合相色谱-串联质谱法测定口含烟中对羟基苯甲酸酯

建立了QuEChERS-超高效合相色谱-串联质谱法（UPC²-MS/MS）测定口含烟中对羟基苯甲酸酯类防腐剂。采用乙腈提取,基质分散固相萃取净化,UPC^{2 TM} HSS C18 SB色谱柱（3.0 mm×100 mm×1.8 μm）分离,内标法定量。优化后的对羟基苯甲酸酯的合相色谱分离条件为：主要流动相为CO₂,改性剂为甲醇-异丙醇混合溶液（V/V,1∶1）,系统流速1.5 mL/min,离子化辅助溶剂（补偿溶剂）为0.1%甲酸-甲醇溶液,动态备压1.03×10⁷ Pa,柱温55 ℃,可在3 min内完成单个样品分析。4种成分的线性范围均为0.5~5.0 mg/kg;在低、中、高加标水平下,方法的平均回收率为94.6%~105.6%,相对标准偏差小于5%。实际样品测定结果表明,单个成分的含量和多种成分的总含量均小于10 mg/kg,低于GB 2760-2014对于此类防腐剂在食品中添加限量的要求。该方法环境友好、高效、准确,适用于口含烟中对羟基苯甲酸酯类物质的测定。     

平面变形回弹迭代补偿的收敛准则及应用

针对板材平面变形过程中的回弹问题,基于迭代法建立了迭代补偿机制,给出了迭代参量收敛性的判定准则。对于简单应力状态下平板单向拉伸和双向拉伸的弹塑性变形过程,证明了参量轴向长度对迭代补偿机制具有收敛性。对于宽板V形自由弯曲工艺,通过理论和实验验证了弯曲曲率和弯曲角的收敛性。进而,将迭代补偿机制应用于宽板自由弯曲工艺的回弹控制,对曲率和弯曲角分别进行了迭代补偿实验,结果表明,根据每次试验的回弹量,迭代补偿机制可以预测下一次补偿值,使弯曲工艺经过2～3次迭代,就获得了误差小于0.1%的目标曲率和误差小于0.5%的目标弯曲角,收敛速度很快。而且,对于同一材料的同一成形工艺,每次的补偿量只取决于回弹前后的迭代参量差值。     

随机环境中具有迁移的两性分枝过程的极限性质

在独立同分布的随机环境下,给出随机环境中具有迁移的两性分枝过程[Z_n,n≥0],并且迁移人口数与当前人口数有关。本文引入每个配对单元的条件均值增长率,讨论增长率的性质,得到该过程条件均值的上下界,研究了过程由此上下界规范化过程的极限性质。     

线性跟踪系统Lyapunov函数性质及其应用

研究了线性跟踪系统Lyapunov函数性质,并基于该性质进行控制系统设计研究,给出控制器结构和Lyapunov函数取值估计;首先,以经典三回路为基础建立线性闭环跟踪系统微分方程;在完成系统数学模型的基础上,给出线性跟踪系统Lyapunov函数对时间的一阶导数为非负,二阶导数为非正,即线性跟踪系统Lyapunov函数最大值不是在系统的初始状态而是稳定状态这一论点;进而基于该Lyapunov函数性质对控制系统进行设计和Lyapunov函数取值进行研究;最后通过仿真验证,仿真结果表明所提出的线性跟踪系统Lyapunov函数性质、控制器设计和Lyapunov函数取值估计是正确的。     

QC-LDPC码的截短技术研究

可变码率编码是现代移动通信系统的一项关键技术。在分组码中,截短(short-ening)技术是实现这一目的主要方法之一。截短是一种通过将一些信息比特用预先约定好的值置换,从而将这些比特的置信度设为无限大的技术。通过该技术,可以缩短码长并降低码率,同时提高码字的性能。针对非规则QC-LDPC码,结合PEXIT分析方法,给出了一种优化地选取截短比特的方法。仿真结果和分析表明,本文的方法使得截短后的码字取得良好的译码性能。     

Light scattering of ideal random copolymers in bulk

Copolymerization is a useful way of modifying the physical properties of a material to meet specific needs, but it can result in a significant light scattering loss due to dielectric fluctuations in the material. Ideal random copolymers are known to be more transparent; however, the light-scattering properties of such copolymers in bulk have not been fully studied. In this paper, two representative ideal random copolymers were synthesized: methyl methacrylate (MMA)/benzyl methacrylate (BzMA) and MMA/2,2,2-trifluoroethyl methacrylate (TFEMA). The effects of copolymer composition and polymerization temperature on the light-scattering properties were investigated. Polarized light scattering (V_V) in copolymers was more sensitive to the polymerization temperature. Higher temperatures were necessary to homogenize the dielectric fluctuations and minimize excess light scattering. However, once the heterogeneous structures vanished, the copolymer bulk exhibited low scattering losses, which are comparable with homopolymers, over the entire range of copolymer compositions.     

“双碳”背景下现代煤化工高质量发展研究

“双碳”目标的提出指明了绿色低碳、清洁高效是能源发展的方向。现代煤化工是煤炭清洁转化利用的有效方式,对保障国家能源安全有重要战略意义,但仍属于高碳排放产业,探寻煤化工高端化、低碳化、多元化发展路径迫在眉睫;分析了现代煤化工产业发展现状及面临的挑战,认为通过坚持科技创新,推进煤化工与其他产业协同融合发展,可以加快现代煤化工产业转型升级,实现高质量发展。     

中国建筑废弃物区域差异及收敛性研究

Construction and Demolition Waste（ C&DW） reduction management is crucial to the sustainable development of theconstruction industry. Based on the calculation of C&DW emissions in China from 2005 to 2018, the Theil index is used to calculatethe intra-regional disparities, inter-regional disparities, and overall Theil index of C&DW emissions in different regions. Theconvergence analysis of C&DW emissions in different regions is also conducted. The results show that the C&DW emissions areregionally significant, showing the overall characteristics of "the C&DW emissions in the east is higher than the west ". Moreover,the C&DW emissions in China are in a relatively stable state of development, difference in regional and overall development aresmall, with conditional β convergence across regions. The research results aim to explore the spatial difference of C&DW emissionsand provide a reference for the government to formulate regional differentiated C&DW reduction management policies.