The role of polyurethane foam compressible layer in the mechanical behaviour of multi-layer yielding supports for deep soft rock tunnels

The polyurethane foam(PU)compressible layer is a viable solution to the problem of damage to the secondary lining in squeezing tunnels.Nevertheless,the mechanical behaviour of the multi-layer yielding supports has not been thoroughly investigated.To fill this gap,large-scale model tests were conducted in this study.The synergistic load-bearing mechanics were analyzed using the convergenceconfinement method.Two types of multi-layer yielding supports with different thicknesses(2.5 cm,3.75 cm and 5 cm)of PU compressible layers were investigated respectively.Digital image correlation(DIC)analysis and acoustic emission(AE)techniques were used for detecting the deformation fields and damage evolution of the multi-layer yielding supports in real-time.Results indicated that the loaddisplacement relationship of the multi-layer yielding supports could be divided into the crack initiation,crack propagation,strain-hardening,and failure stages.Compared with those of the stiff support,the toughness,deformability and ultimate load of the yielding supports were increased by an average of 225%,61%and 32%,respectively.Additionally,the PU compressible layer is positioned between two primary linings to allow the yielding support to have greater mechanical properties.The analysis of the synergistic bearing effect suggested that the thickness of PU compressible layer and its location significantly affect the mechanical properties of the yielding supports.The use of yielding supports with a compressible layer positioned between the primary and secondary linings is recommended to mitigate the effects of high geo-stress in squeezing tunnels.

Layered zirconium phosphate-supported metalloporphyrin:Synthesis and catalytic application

This paper reports a new route for the preparation of layered alpha-zirconium phosphate （α-ZrP）-supported metalloporphyrin MnTMPyP. MnTMPyP was intercalated into α-ZrP using α-ZrP.BA （i.e. pre-intercalated bultylamine was arranged by a monolayer mode in α-ZrP） as a starting material. The catalytic activity of the supported material for homovanillic acid （HVA） oxidation was investigated. The results showed a promising layered material-supported catalyst in catalytic system.

Layered double hydroxide-like Mg_3Al_(1–x)Fe_x materials as supports for Ir catalysts: Promotional effects of Fe doping in selective hydrogenation of cinnamaldehyde

Supported Ir catalysts were prepared using layered double hydrotalcite‐like materials,such as Mg3Al1-xFex,containing Fe and Al species in varying amounts as supports.These Ir catalysts were applied for the selective hydrogenation of cinnamaldehyde(CAL).When x was changed from 0(Ir/Mg3Al)to 1(Ir/Mg3Fe),the rate of CAL hydrogenation reached a maximum at approximately x=0.25,while the selectivity to unsaturated alcohol,i.e.,cinnamyl alcohol,monotonously increased from 44.9%to 80.3%.Meanwhile,the size of the supported Ir particles did not change significantly with x,remaining at 1.7-0.2 nm,as determined by transmission electron microscopy.The chemical state of Ir and Fe species in the Ir/Mg3Al1-xFex catalysts was examined by temperature programmed reduction by H2 and X‐ray photoelectron spectroscopy.The surface of the supported Ir particles was also examined through the in‐situ diffuse reflectance infrared Fourier‐transform of a probe molecule of CO.On the basis of these characterization results,the effects of Fe doping to Mg3Al on the structural and catalytic properties of Ir particles in selective CAL hydrogenation were discussed.The significant factors are the electron transfer from Fe2+in the Mg3Al1–xFex support to the dispersed Ir particles and the surface geometry.

Elastic Modulus Limit of Support Layer in Twin-Block Ballastless Track Based on Train Load Effect

The support layer is an important component of twin-block ballastless track. The modulus of the support layer is an important design parameter and must be carefully solved. We studied the bending stress and deformation of track slab and support layer due to train load using the beam-plate finite element model on elastic foundation. The results show that support layer type has great impact on both support layer deformation and the stress on subgrade, but has little impact on the bending stress of either track slab or support layer. The continuous support layer type, and articulated support layer type with shear transfer device at their ends, are recommended. In order to keep the stress in the support layer less than that in track slab, the modulus of the continuous, unit, and articulated types of support layer （ in unit twin-block ballastless track）, and the support layer in continuous twin-block ballastless track, should not be larger than 15, 22, 20.5 and 5 GPa, respectively. In addition, the modulus of the unit-type support layer should not be more than 20 GPa, to ensure the step in support layer remains less than 1 mm.

Metal–organic-framework derived supporting layers for highly efficient CdSe QDSSCs

Metal–organic-framework(MOF)has been an increasingly hot organic-inorganic hybrid compounds. Here we develop an innovative concept by engineering a supporting layer made of MOF derived carbon materials. The supporting thin layer is prepared by carbonizing zeolitic-imidazole framework(ZIF-67). CdSe quantum dot sensitized TiO_2 nanocrystalline thin film deposited by the method of chemical bath deposition(CBD). The MOF unique microstructure in the support layer builds the electronic highway, which greatly improves the efficiency of the CdSe quantum dot-sensitized solar cells(QDSSCs), and the power conversion efficiency(PCE)of the device was significantly improved from 2.98% to 5.79% via ZIF-67 derived carbon supporting thin layer.

Building up Multi－Layered Perceptrons as Classifier System for Decision Support

This paper focuses on some application issues in m.multi-layered perceptrons researches. The following problem areas are discussed: (1) the classification capability of multi-layered perceptrons; (2) theself-configuration algorithm for facilitating the design of the neural nets' structure;and,finally (3) the application of the fast BP algorithm to speed up the learning procedure. Some experimental results with respect to the application of multi-layered perceptrons as classifier systems in the comprehensive evaluation of Chinese large cities are presented.

Modification of rock mass rating system:Interbedding of strong and weak rock layers

Rock mass classification systems are the very important part for underground projects and rock mass rating(RMR) is one of the most commonly applied classification systems in numerous civil and mining projects. The type of rock mass consisting of an interbedding of strong and weak layers poses difficulties and uncertainties for determining the RMR. For this, the present paper uses the concept of rock bolt supporting factor(RSF) for modification of RMR system to be used in such rock mass types. The proposed method also demonstrates the importance of rock bolting practice in such rock masses. The geological parameters of the Shemshak Formation of the Alborz Tunnel in Iran are used as case examples for development of the theoretical approach.

Double-layer Bayesian Classifier Ensembles Based on Frequent Itemsets

Numerous models have been proposed to reduce the classification error of Naive Bayes by weakening its attribute independence assumption and some have demonstrated remarkable error performance. Considering that ensemble learning is an effective method of reducing the classifmation error of the classifier, this paper proposes a double-layer Bayesian classifier ensembles （DLBCE） algorithm based on frequent itemsets. DLBCE constructs a double-layer Bayesian classifier （DLBC） for each frequent itemset the new instance contained and finally ensembles all the classifiers by assigning different weight to different classifier according to the conditional mutual information. The experimental results show that the proposed algorithm outperforms other outstanding algorithms.

Shaking table test and numerical simulation of an isolated cylindrical latticed shell under multiple-support excitations

In order to study the infl uence of the ground motion spatial eff ect on the seismic response of large span spatial structures with isolation bearings, a single-layer cylindrical latticed shell scale model with a similarity ratio of 1/10 was constructed. An earthquake simulation shaking table test on the response under multiple-support excitations was performed with the high-position seismic isolation method using high damping rubber (HDR) bearings. Small-amplitude sinusoidal waves and seismic wave records with various spectral characteristics were applied to the model. The dynamic characteristics of the model and the seismic isolation eff ect on it were analyzed at varying apparent wave velocities, namely infi nitely great, 1000 m/s, 500 m/s and 250 m/s. Besides, numerical simulations were carried out by Matlab software. According to the comparison results, the numerical results agreed well with the experimental data. Moreover, the results showed that the latticed shell roof exhibited a translational motion as a rigid body after the installation of the HDR bearings with a much lower natural frequency, higher damping ratio and only 1/2~1/8 of the acceleration response peak values. Meanwhile, the structural responses and the bearing deformations at the output end of the seismic waves were greatly increased under multiple-support excitations.

A problem solving framework for group decision support system

A new problem solving framework for group decision support system using layer model approach is proposed. This kind of framework includes four basic layers, namely, application layer, task layer, logical layer and physical layer. Based on indicating the respective meanings of those layers a task skeleton of group decision support system and a logical structure of group decision support system generator are put forward and discussed in detail. The framework provides theoretical guidance for developing group decision support system to lower systematic development complexity and support reuse of software.

基于多层耦合网络的装备保障体系级联失效及抗毁性分析

为准确描述装备保障体系结构特征与毁伤失效流程,进而提升装备保障体系功能与抗毁能力,基于杀伤层、保障层和储供层构建装备保障体系的多层耦合网络模型。基于杀伤链给出装备维修保障链与储供保障链的特征和典型样式,在此基础上,提出考虑装备保障体系多层耦合网络特性的级联失效模型与节点重要度评估方法。给出对应的网络抗毁性评估指标。仿真结果表明,考虑级联失效的多层耦合网络模型能较好地反映遭受攻击时整个装备保障体系的性能变化情况,所提出的使命任务节点重要度能准确识别关键节点。与传统网络抗毁性指标相比,杀伤链数量对节点失效产生的装备保障体系抗毁性变化更加敏感。

基于CNN-SVM模型的鸡蛋外观品质检测

[目的]提高鸡蛋外观品质检测的精度,建立CNN-SVM模型的鸡蛋外观品质检测模型。[方法]结合CNN的自适应特征提取功能和SVM的超强泛化分类性能,通过6层卷积神经网络结构处理提取全连接层的特征,采用CNN-SVM混合模型替代传统CNN+softmax,构建一个基于CNN-SVM模型的鸡蛋外观品质检测方法。[结果]与SVM模型、CNN模型和KNN模型相比,CNN-SVM模型在准确率、精确率、召回率和F1分数方面表现优异,分别为97.97%,98.10%,98.10%,98.00%。KNN模型在鸡蛋外观品质检测上的精度最低,其准确率、精确率、召回率和F1分数分别为77.46%,79.44%,76.75%,76.90%。[结论]CNN-SVM模型具有很强的鲁棒性和抗噪声能力,可以有效提高鸡蛋外观品质检测的准确性和适用性。

基于总安全系数法的喷射混凝土支护承载能力的试验研究

为验证总安全系数法中喷层的荷载结构模型及其安全系数计算方法,研制大型隧道结构模型试验系统,采取结构试验的方法,开展毛洞、不同厚度喷层以及二次衬砌的加载破坏试验。通过围岩和细砂材料的三轴试验明确模型试验中各材料的物理与力学参数,模拟毛洞、不同厚度喷层以及二次衬砌的加载破坏全过程,依据破坏状态明确喷层与二次衬砌的设计承载能力,试验中监测围岩应力应变、喷层内外侧应变和喷层位移,结合监测结果分析喷层与二次衬砌在承载过程中的变形特征与受力特征,明晰喷层与二次衬砌的承载机制,并与总安全系数法理论计算结果进行对比分析。结果表明:1)在试验断面条件下喷层受力状态为小偏心受压,喷层与围岩之间的粘结能有效传递剪力,从而减少了喷层的弯矩,有利于充分发挥喷层的抗压强度,同厚度情况下喷层的设计承载力要高于二次衬砌;2)试验得到的厚度为2 cm和4 cm喷层的设计承载力比总安全系数法理论计算结果分别大27.0%和22.9%,表明总安全系数法的喷层承载力计算模型是合理的,并具有合适的安全性。

双层索系柔性光伏支架结构受力性能研究

目的研究双层索系柔性光伏支架结构在风荷载作用下的静力性能与动力响应。方法采用ABAQUS有限元软件开展双层索系柔性光伏支架结构的静力性能、动力特性、动力响应和风振系数分析,探究了跨度、横向连接系间距以及挠度限值等影响因素对支架结构受力性能的影响。结果结构的风振响应随着跨度的增加而增大;结构跨中挠度及上层索索力随横向连接系间距的增大而增大;增大上层索预应力可以减小结构的动力响应,而下层索预应力过大会导致结构的风振响应增大。结论通过研究给出了双层索系柔性光伏支架结构的风振系数取值范围以及上、下层索的初始预拉力设置建议,可以为其结构抗风设计提供参考。

Status epilepticus increases mature granule cells in the molecular layer of the dentate gyrus in rats

Enhanced neurogenesis in the dentate gyrus of the hippocampus following seizure activity, especially status epilepticus, is associated with ectopic residence and aberrant integration of newborn granule cells. Hilar ectopic granule cells may be detrimental to the stability of dentate circuitry by means of their electrophysiological properties and synaptic connectivity. We hypothesized that status epilepticus also increases ectopic granule cells in the molecular layer. Status epilepticus was induced in male Sprague-Dawley rats by intraperitoneal injection of pilocarpine. Immunostaining showed that many doublecortin-positive cells were present in the molecular layer and the hilus 7 days after the induction of status epilepticus. At least 10 weeks after status epilepticus, the estimated number of cells positive for both prospero homeobox protein 1 and neuron-specific nuclear protein in the hilus was significantly increased. A similar trend was also found in the molecular layer. These findings indicate that status epilepticus can increase the numbers of mature and ectopic newborn granule cells in the molecular layer.

基于多层全连接神经网络的6C地震波极化向量识别研究

利用机器学习原理,提出一种基于多层全连接(multi-layer fully connected, MFC)神经网络的六分量(six-component, 6C)地震波极化向量识别方法。首先利用6C地震波各波型极化向量数学模型和一系列仿真参数得到5种波型和噪声波型各5 000个极化向量数据集,然后随机选取其中5 000个作为测试集,其余划分为训练集,进行MFC神经网络与支持向量机(support vector machine, SVM)的综合辨识性能对比实验。结果表明,MFC神经网络模型识别5种极化向量类型(SH波和Love波视为一类)和6种极化向量类型的效果均显著优于SVM模型,平均识别率分别达到99.786%和87.940%。

错层位外错式巷道位置选择及联合支护研究

针对新巨龙煤矿1301综放工作面区段间留设煤柱尺寸较大造成的资源浪费和回采巷道支护困难等问题,本文提出采用错层位外错式巷道布置方案,建立错层位非常规煤柱力学模型,利用极限平衡理论分析了非常规煤柱应力环境和极限平衡区特征;考虑不同错距下沿底巷道所处应力环境及区段煤柱弹性应变能密度分布特征,确定下区段沿底巷道合理错距为3.0 m;同时引入区段间相邻巷道联合支护方案,对实际地质条件下接续工作面回采阶段区段间相邻巷道联合支护方案和传统支护方案进行模拟验证。结果表明:区段间相邻巷道联合支护方案优于传统支护方案,峰值应力由80 MPa降至64 MPa,降低率为20%,表明其对巷道围岩控制更为有效;区段煤柱单位留设面积为111.5 m^(2),相较于传统支护方案区段煤柱的170 m^(2),降低率为34.4%。研究结果对减少区段煤柱留设尺寸和提高煤炭回采率起到积极的推动作用。

分叉柱支承式单层曲面钢网壳施工过程监测研究

以云南红河综合交通枢纽单层曲面网壳为工程背景,对网壳结构、提升塔架的关键杆件布置测点进行施工过程监测研究,分析了结构在地面拼装及整体提升过程中内力的变化情况。通过对施工过程中网壳结构的温度效应进行研究,探讨了边界约束作用强弱对结构内力变化的影响程度,温度每变化1℃引起的网壳合拢后应力变化是合拢前应力变化的3倍;合拢后,温度每变化1℃引起网壳远离支座杆件的应力变化是靠近支座应力变化的2倍;对提升阶段监测数据进行分析,提升过程中实测应力波动范围在10 MPa以内,吊点提升同步性较好;此外,网壳结构卸载阶段监测数据表明,由于网壳提升状态与使用状态受力基本一致,网壳卸载前后应力变化较小,且卸载后支撑结构对温度敏感性较高。

特厚煤层沿空掘巷围岩支卸协同控制技术

针对特厚煤层小煤柱沿空掘巷大范围塑性全煤巷道锚网索的支护难题,以塔山煤矿8204-2小煤柱工作面为工程背景,采用现场实测、理论分析等方法,揭示了锚杆、锚索对沿空大范围塑性全煤巷道的支护机理。锚杆支护主要作用于浅部二次破碎区煤体,形成浅部连续承载结构;锚索主要作用于深部处于三向受力状态的稳定煤体,形成更大范围的连续稳定承载结构;进一步明确了锚杆、锚索有效长度的计算方法,形成了以高预紧力、高强“锚-网-索”支护为基础,以坚硬顶板井下磨料水射流切顶卸压、巷帮大直径钻孔卸压、底板卸压槽卸压为辅的“支卸协同”小煤柱沿空巷道围岩控制技术体系。工程应用结果表明,试验巷道围岩最大变形量小于700 mm,能够满足使用要求。

层台累榭--楚国建筑形制特征探讨

两周时期楚国作为南方长江流域的霸主国家独领风骚,楚文化源于北方中原的商周文化,发展壮大于南方楚地,得天独厚的自然环境是孕育楚文化的重要基础。基于此,该文首先分析了楚文化及其自然环境的独特特征。其次,推论影响楚建筑形制的因素,提出其在楚文化与楚地自然环境影响下产生发展了楚高台建筑与干阑建筑。最后以文献和考古记载中的楚宫建筑为例,探讨楚国建筑“层台累榭”之形制特征。