课程文献中心 更多>>

关键词： Moho   Crust-mantle transition zone   Velocity contrast   Multiband receiver functions  

摘要： The crust-mantle transition zone is the boundary layer between the crust and mantle. The fine structure feature of the transition zone, including its thickness, velocity and density contrast across it, provides important constraints on the material and energy exchange between the lower crust and the top of the upper mantle. Conventional studies simplify the crust-mantle transition zone as a first-order discontinuity (i.e., Moho) to estimate seismic property differences between adjacent media, yet this simplification may introduce substantial bias. Based on numerical experiments, this study proposes a method to simultaneously determine the S-wave velocity contrast across the crust-mantle transition zone and the transition width using amplitude of Pms converted phase from multiband receiver functions. We apply the method to teleseismic data recorded by 47 permanent stations in the Sichuan-Yunnan area. The results show that the crust-mantle transition zone in the Sichuan basin is thin with a low velocity contrast, indicative of typical cratonic characteristics, suggesting that little difference between the lower crust and upper mantle materials in this area. The crust-mantle transition zone in the Songpan-Garz & ecirc;block is thin with a high velocity contrast, suggesting partial melting near the bottom of the crust. The Kangding block and the west side of the Central Yunnan block are characterized by a thick crust-mantle transition zone, suggesting the existence of mantle material upwelling and bottom intrusion in this area. The crust-mantle transition zone in the Emei Mountain area on the southwestern edge of the Sichuan basin has a high velocity contrast, suggesting that there is partial melting in the lower crust in this area. The crust-mantle transition zone under the JYA station is thick, which may be due to the drastic lateral variation of the crust-mantle transition zone depth which blurred its upper and lower boundaries.

关键词： one-pot   metal-free   Ugi 4CR   alkyne-azide cycloaddition   1,2,3-triazolobenzodiazepinone  

摘要： A novel and metal-free sequential Ugi-4CR/alkyne-azide cycloaddition reaction towards the synthesis of new 1,2,3-triazolobenzodiazepinones under a mild reaction is reported. The reaction of (E)-2-(1-alkynyl)-3-arylpropenoic acids, 2-azidobenzenamines, aldehydes, and isocyanides produced 1,2,3-triazolobenzodiazepinones by a Ugi 4CR/alkyne-azide cycloaddition sequence in excellent yields ranging from 77% to 92%. Furthermore, simple operation, high atom economy and good to excellent yields all make it useful in synthetic and medicinal chemistry.

关键词： Resistivity method   Anisotropic medium   Forward modelling   Green function   Total potential  

摘要： Under natural conditions, certain metal ore deposits are situated within sedimentary and metamorphic rock formations. As a result of sedimentary cycles and tectonic compression, most sedimentary rocks and some metamorphic rocks exhibit a stratified structure, with their conductivity displaying significant anisotropy. In specific instances, the resistivity rho(n) perpendicular to the bedding direction is several times greater than the resistivity rho(t) along the bedding direction. The anisotropic nature of rock layers distorts the ideal (uniform and isotropic) electric field distribution pattern under ideal conditions, directly leading to complexities in subsequent interpretation and inference work in electrical prospecting. Consequently, this paper undertakes 3D resistivity forward modeling for anisotropic conductive media. Firstly, it introduces scalar Green's function to form a novel expression for Green's function in anisotropic media, eliminating singularity near point current sources while achieving numerical simulation of total electric potential response in anisotropic geoelectric models;secondly, it verifies computational accuracy of proposed algorithms using uniform half-space anisotropic models;subsequently defining anisotropic apparent resistivity and demonstrating algorithm applicability through Wenner profile curves on vertical direct contact surfaces;finally calculating apparent resistivity for underground square target body deposits to examine influence of non-isotropic medium conductivity on resistivity responses while identifying subsurface medium's anisotropic characteristics. Modeling results indicate that this study not only reduces complexity of traditional algorithms but also significantly enhances calculation accuracy expected to be actively applied across other branches of electromagnetic exploration methods.

关键词： 优化   过程控制   自优化控制   控制结构   连续重整   代理模型   动态仿真  

摘要： 首先,提出了一种全局自优化控制(gSOC)问题的代理模型构建策略.该策略针对gSOC问题的特殊性,融合了划分空间设计和子模型混合自适应采样方法,提升了构建效率.在此基础上,对gSOC算法流程进行了优化,加速了最优组合矩阵的求解,扩展了算法对复杂和大规模过程的适用性.其次,改进后的算法应用于连续重整(CCR)反应过程的控制结构设计.通过结合改进的gSOC算法与模拟和启发式集成框架,系统地分析和设计了 CCR反应过程的自优化控制结构,缓解了进料性质、循环氢流量及反应器入口温度的参数不确定性扰动与故障带来的芳烃损失.最后,动态模拟实验结果表明,所设计的SOC结构表现出显著的实时优化性能.该研究为工业CCR装置的控制提供了理论指导.

关键词： 预应力混凝土   连续箱梁桥   裂缝成因   控制  

摘要： 预应力混凝土连续箱梁桥结构应用广泛.然而,预应力混凝土连续箱梁桥可能会在使用期间出现不同性质的裂缝.这不仅会影响桥梁的外观,还会导致桥梁的刚度分布出现问题.通过分析预应力混凝土连续箱梁桥裂缝的成因,如施工中承受荷载过大、施工期间预应力混凝土相关条件控制低下、施工材料选择缺乏科学合理性等,提出创新连续箱梁桥设计并增强预应力结构稳定性、合理控制预应力混凝土浇筑范围、合理选择施工材料等针对性控制策略,旨在推动桥梁工程的高质量发展.

关键词： 简支钢混组合梁   桥面连续结构   无粘结桥面连接板   足尺试验   静力性能  

摘要： 为研究一种新型桥面连续结构的静力性能，设计了一个足尺工字形钢混组合梁节段试验模型，采用了一套竖向主动加水平随动的加载系统来模拟桥面连接板的受力状态，测试了混凝土和钢筋的应变、试件的变形及裂缝的发展。试验结果表明：（1）该结构具有良好的静力性能，试件的破坏形式为延性的弯拉破坏，破坏时连接板的受拉钢筋屈服，混凝土未压溃；（2）连接板的裂缝基本沿着桥面连接板横桥向直线发展，分布形态是典型的弯拉开裂的裂缝形态；（3）在最大裂缝宽度达到0.4mm时，整个桥面连续构造的开裂范围局限于桥面连接板范围内，这将很有利于后期养护维修。本文结合桥梁规范对试验所得的最大裂缝宽度和极限荷载进行分析，结果表明：（1）桥面连接板的最大裂缝宽度应按规范中的偏心受拉构件计算，正常使用极限状态下，对应实桥的弯矩与轴力计算值是安全的；（2）桥面连接板的抗弯承载力可按规范计算，连接板极限弯矩试验值与计算值的比值为1.2。

关键词： 车辆工程   轴箱轴承   故障诊断   加权自相关函数能量熵   最大重叠离散小波包变换  

摘要： 针对轴箱轴承早期微弱故障特征易被轮轨噪声淹没进而导致难以提取这一问题，提出了一种基于加权自相关函数能量熵谱图的轴箱轴承故障诊断方法。首先，基于最大重叠离散小波包变换对原始信号进行划分得到子频带。其次，计算各子频带的自相关函数能量熵，并将子频带峭度与原始信号峭度的比值作为其权重。然后，分别以所有分解层数中的平均加权自相关函数能量熵最大值及该层中所有子频带中的加权自相关函数能量熵最大值自适应确定最优分解层数及频带。基于轴箱轴承仿真信号的分析结果表明，本文所提方法能够有效避免谐波噪声及踏面缺陷损伤冲击引起的背景噪声干扰。最后，分别采用机车及客车轴箱轴承试验数据对本文所提方法的有效性和优越性进行了验证。

关键词： 钢混组合梁桥   挠度影响线   模型修正   PSO-BP代理模型   非支配排序遗传算法  

摘要： 为突破静力或动力单指标参数对模型修正研究的局限性，提出一种基于频率与影响线双目标优化的桥梁模型修正方法，通过钢混组合连续梁桥试验进行了方法可行性与实用性验证。首先对桥梁在环境激励下进行模态测试，采用增强频域分解方法获取前三阶频率，再利用单辆重车怠速移动加载激励，测得中跨跨中截面挠度时程响应，结合变分模态分解与Tikhonov正则化剥离车致响应动力成分与车辆多轴效应，得到桥梁挠度影响线。利用频率与挠度影响线构造联合目标函数，选择合理待修参数构建PSO-BP代理模型并结合带精英策略的快速非支配排序遗传算法对有限元模型进行双目标修正，得到双目标优化问题下的Pareto协调最优解，并通过现场实测数据对修正后的模型进行精度验证。结果表明：修正后模型基频相对误差由17.6%降低至3.27%；挠度影响线整体相对误差由39.7%降低至16%，控制截面处峰值相对误差由41.1%降低至3.55%，故面向频率与影响线双目标优化的模型修正方法可以大幅提升修正后模型精度，更加贴近实际桥梁状态，为进一步开展精细模拟奠定基础。

关键词： 盾构   连续穿越   高铁群桩   施工   Boltzmann函数模型   Poly函数模型  

摘要： 为保障地铁盾构隧道在近距离连续穿越高速铁路桥梁群桩过程中的铁路运营安全，以某实际下穿高铁群桩工程为背景，采用有限元数值模拟与现场监测相结合的方法，系统分析了盾构区间双线连续穿越多线路高铁桥梁群桩的施工全过程响应。结果表明：现场施工引起的高铁桥墩附加变形处于严格可控范围内，桥墩最大竖向位移为－0.75 mm，最大顺桥向位移为－0.67 mm，最大横桥向位移为0.18 mm，数值模拟结果与实测数据高度吻合，验证了模型可靠性。施工完成后，桥墩竖向位移呈“中间大、两侧小”的分布特征，其中3号墩因受双线盾构叠加效应影响位移最大；顺桥向位移表现为2、4号墩较大，3号墩因双线位移相互抵消而最小；横桥向位移整体数值较小。进一步通过位移回归函数分析表明，Boltzmann函数模型对桥墩竖向及顺桥向位移具有优异的预测精度，Poly函数模型则适用于横桥向位移的拟合。实践表明，采用加强配筋管片设计、增设注浆孔、克泥效工法及分序掘进等综合控制措施，可有效抑制地层扰动与桥墩变形。

关键词： 数论函数   广义Euler函数   Smarandache LCM函数   Smarandache函数   可解性  

摘要： 数论函数方程是数论研究的主要内容之一。本文利用Euler函数φ（n）、Smarandache函数S（n）、Smarandache LCM函数SL（n）、广义Euler函数φ2（n）的定义与性质，以及初等的方法和技巧，结合分类讨论的思想，研究了形如φ（n）+S(SL(nl))=kφ2（n）的数论函数方程的可解性， 得到了包含Smarandache LCM函数等的数论函数方程φ（n）+S(SL(n9))=kφ2（n）有35组正整数解。