双曲线冷却塔风筒几何缺陷分析

由于施工放样原因,双曲线冷却塔风筒发生移位变形,筒壁出现初始几何缺陷,偏差超出规范允许值,造成冷却塔应力状态改变.利用冷却塔专用计算软件对冷却塔结构进行静力计算,根据计算的内力对强度进行验算,分析初始几何缺陷对冷却塔应力状态的影响,评价冷却塔结构安全性及是否需要进行加固处理,并对冷却塔后期维护提出建议.     

Modeling deterministic echo state network with loop reservoir

Echo state network (ESN),which efficiently models nonlinear dynamic systems,has been proposed as a special form of recurrent neural network.However,most of the proposed ESNs consist of complex reservoi...     

FPGA设计中的亚稳态及其缓解措施

亚稳态是异步数字电路设计中的固有现象。针对FPGA产品研制中的亚稳态问题,分析了其产生的原因,阐述了亚稳态对系统可靠性的影响和评估方法,并针对单比特异步传输、多比特异步传输和复位三种情况下的亚稳态提出缓解措施。该措施可以在工程实践中参考使用。     

基于李雅普诺夫函数法的扩张状态观测器参数优化

针对ESO参数不易整定的问题,研究了扩张状态观测器(ESO)参数优化的李雅普诺夫函数法.首先建立关于误差的线性定常状态方程和误差指标函数J,在误差指标函数J中综合考虑了跟踪误差的权重和系统的稳定性以及实际运行时的饱和值限制等因素.仿真结果表明,此方法具有概念清晰,实用简便,计算量小的优点.所提ESO参数整定方法是有效的.     

A RIS treatment of the mean-square dipole moment of PMMA chains in consideration of the pendant ester group orientations

According to the six-state scheme proposed by Vacatello and Flory, the mean-square dipole moments 〈M²〉/x (x: number of monomeric units) of poly(methyl methacrylate) (PMMA) chains and their temperature dependence were calculated by the matrix algebra method of rotational isomeric state theory. To take account of the orientation effect of polar ester groups, the statistical weight matrices, U′ and U″, were recast into an expanded form. A Bernoullian probability λ introduced to measure the preference between the two alternative orientations (χ=0 and χ=π) of the side ester groups was found to give rise to a large effect on the mean-square dipole moment of polymers. When the skeletal bonds of a meso dyad are both in trans, an exceptionally strong dipole-dipole interaction may take place. If the two adjacent ester groups adopt the same orientation, the dipoles must be situated nearly parallel to each other in a close proximity. Such repulsive interactions may be alleviated by taking a staggered conformation, i.e. (χ,χ′)=(0,π) or (π,0). Such neighbor-dependent correlation inherent to the meso dyad is considered by assigning a parameter λ′ to the proper element of the U_m″ matrix. The values of 〈M²〉/x observed at 30 °C were satisfactorily reproduced by adopting λ=0.270 and λ′=0.865. The thermal coefficients were found to be reconciled with the available experimental data by allowing the orientation parameters λ and λ′ to be slightly temperature dependent. The stereochemical characteristics of the chain terminals were examined in order to extend the treatment to include the dipole moment of PMMA oligomers.     

水口水电厂设备状态监测与诊断分析系统

结合工程实践,全面地描述了水口水电厂机组、主变的状态监测与诊断分析系统,包括总体目标和设计原则,系统总体结构,监测范围和测点布置,软件系统组成,系统的主要功能及应用。     

聚氨酯基pH/温度敏感性水凝胶的结构形态

通过阴离子型端丙烯酸酯基聚氨酯(UAA)与N-异丙基丙烯酰胺(NIPAAm)的共聚交联反应,制备了pH/温度敏感性水凝胶,分析了水凝胶的结构形态及溶胀水的状态.结果表明,凝胶相结构均匀,随聚氨酯含量的降低,凝胶的骨架变得松散,并且孔道结构增大,导致溶胀凝胶中不可冻结水含量及凝胶强度的降低.     

陶瓷基复合材料伪半固态触变成形及其在卫星角框件中的应用

提出了陶瓷基复合材料伪半固态成形工艺,并应用该工艺制备了30%(体积分数)Alp/SiCp复合材料卫星角框件.通过金相分析、拉伸等实验方法验证该工艺的可行性.结果表明,该工艺成形的零件微观组织比较均匀;硬度较高,HV可达到6.43GPa;应变(ε)约为0.5%;抗拉强度(σt)约为300MPa.     

基于van der Waals状态方程的剩余自由能模型

结合 Wong- Sandler的混合规则 ,即在无穷大压力下剩余 Helmholtz自由能与无穷小剩余 Gibbs自由能近似相等的关系 ,给出了一个基于 van der Waals状态方程的剩余自由能模型 ,由此得到可以描述汽液相平衡的活度系数模型。通过对 35个体系的考核表明 ,该模型可以较好的关联实验数据 ,包括极性与极性物系 ,其结果好于 Wilson、Mar-gules、NRTL与 Uniquac等模型的计算结果。同时 ,因为该模型基于 Wong- Sandler的混合规则 ,因此可以实现在理想溶液中 ,由 Wong- Sandler混合规则到 van der Waals混合规则平滑过渡。     

锆合金的碘致应力腐蚀开裂研究(英文)

研究了不同热处理状态的Zr-2和Zr-4合金在不同浓度的碘介质及实验温度下的应力腐蚀开裂(SCC)行为。并对不同织构取向的试样在350℃下进行了蠕变实验,蠕变实验的载荷值选择与SCC实验相对应的一系列典型载荷。用扫描电子显微镜观察了断口特征,用透射电子显微镜和光学显微镜检查了材料的显微组织,用X-光衍射仪测定了锆合金的织构,分析讨论了材料状态、实验温度、碘浓度以及蠕变对锆合金碘致应力腐蚀行为的影响。