PTCR半导陶瓷老化后的复阻抗研究

根据ＰＴＣＲ半导体陶瓷在湿热条件下的老化试验结果，对ＰＴＣＲ半导体陶瓷老化前后分别提出了不同的等效电路模型，通过对阻抗－频率关系曲线的测量，求出了ＰＴＣＲ半导瓷的特性参数．计算结果表明，老化后室温阻值增加，这主要是电极氧化引起的．对实验结果进行了物理本质的初步探讨．     

考虑桩土接触面特性的水平受荷单桩数值分析

采用数值方法研究了桩土接触面特性对水平受荷桩受力特性的影响,并通过对工程实例的分析验证了计算方法的有效性.实例分析表明,设置接触面对于正确模拟桩土受力特性有较大影响.计算所得的桩身弯矩和位移曲线表明,水平受荷桩的入土深度有个临界值,桩身过长对提高水平承载力无明显作用.     

细胞色素C在SAM修饰电极上的电化学行为

应用循环伏安法研究了细胞色素c在2-氨基乙硫醇自组装膜修饰金电极上的电化学行为。结果表明，细胞色素c在2-氨基乙硫醇修饰的金电极上的电子传递过程为—扩散控制的可逆反应，2-氨基乙硫醇自组装膜可用作细胞色素c电子传递的有效促进剂。依据电化学石英晶体微天平和电化学交流阻抗谱的测量结果，讨论了单分子膜的组装过程及其对促进细胞色素c电子传递的作用机制。     

聚苯胺修饰电极的制备与形貌、阻抗表征

运用循环伏安(CV)法制取聚苯胺,结合扫描电子显微镜(SEM)、阻抗谱(EIS)等手段,对聚苯胺的表面形貌及其特征进行研究,并建立了聚苯胺覆盖Pt电极的阻抗模型.实验表明,随着循环次数的增加,聚苯胺膜厚增加,而且所制得的聚苯胺膜呈现多孔、疏松的特征,符合其作为基体材料的特点.     

膜振动理论在纤维材料吸声性能研究中的应用

膜振动理论作为经典声学理论的基础已得到广泛的研究.作者在研究中发现,将膜振动理论的某些结论与毛细管吸声理论结合后,建立的薄纤维层(如织物、无纺布等)吸声理论方程不仅与实验结果吻合较好,而且可以较好的解释薄纤维层在作为护面材料或紧贴墙壁时吸声系数等于或接近于零,而作为窗帘或背后有空腔时却具有较好的吸声效果的这一长期未能解释的声学现象.     

推力桩计算的综合刚度双参数法半数值解

针对现有综合刚度双参数法计算推力桩的幂级数解析解公式较为冗长、编程不便和查表手算较为繁琐的不足,提出结合解析解可取成果反算桩-土综合刚度和地基系数的双参数,再采用分析原理简单、便于编程的有限差分数值计算手段进行桩身位移、侧土抗力和内力计算的新方法.实例计算比较表明,该法方便可靠,对于推广综合刚度双参数法在推力桩计算工程实践中的应用是有益的.     

利用信号与系统概念分析线天线的互阻抗

基于信号与系统理论 ,并利用数字信号处理技术 ,提出了一种分析线天线互阻抗的新方法 .在这种方法中 ,借用信号与系统的概念 ,将天线阵中天线单元的电流视为激励信号 ,将天线阵的空间结构视为系统函数 (或传递函数 ) ,而将单元天线间的互阻抗 (或其它电磁特性 )视为整个系统的响应 .通过这种等效 ,可将天线阵中天线单元间相互耦合看作信号与系统中的系统响应 ,进而可利用数字信号处理方法进行分析 .最后给出了利用该方法计算对称振子天线互阻抗的实例 ,计算结果证明了该方法的有效性 .     

基于传输贡献矩阵的城市路网节点重要性评估方法

 在城市道路中,通常采用交叉口流量或道路连接数等单一指标确定路口重要性,很难保证突发事件下道路网络运行的可靠性。鉴于城市道路网络的无标度特性,以交通阻抗为权重,将城市道路网络抽象为加权网络,提出节点重要度传输贡献矩阵方法,评估道路交叉口重要性。该方法综合考虑交叉口所处路网位置、道路连接数及关联路段交通阻抗,采用节点效率值表示其位置信息,通过融合节点度值和交通阻抗值,构建交通信息传播过程中节点之间的重要度关联,以表示相邻路口间重要性依赖关系。以天津市区域路网为例计算各交叉口重要度,采取连续移除重要节点方式,模拟连锁故障过程,并将结果与节点收缩法进行对比。实证分析表明：在移除最重要的8个节点后,路网最大连通子图规模较节点收缩法降低9.10%,验证了该方法的有效性。     

Optimization of solid phase dispersive field‐assisted ultrasonication for the extraction of auramine O and crystal violet dyes using central composite design

Simultaneous preconcentration and determination of auramine o (AO) and crystal violet (CV) dyes from aqueous solution was conducted by ultrasound assisted (dispersive) solid phase microextraction (UASPME) based on SnO₂/SnS composite loaded activated carbon (SnO₂/SnS‐NCs‐AC). The prepared of SnO₂/SnS‐NCs‐AC was characterized by FESEM and XRD analysis. Main and interaction influences of operational parameters such as pH, sonication time, amounts of sorbent, and type of eluent on extraction efficiency were investigated by central composite design and optimized with desirability function approach (DFA). ANOVA was conducted and shows that optimized values were found at 15.33 min sonication time, 0.019 g SnO₂/SnS‐NCs‐AC mass, pH 5.46 and among different solvents, dimethyl formamide was selected as an efficient eluent. Under this conditions recoverees percentage were obtained 82.85% and 86.70% for AO and CV, respectively. Based on F‐test under ANOVA all main effect and interaction effect of understudy parameters has the significant effect on the responses. At optimum conditions, limit of detection (0.0015 and 0.001 mg/l), limit of quantitation (0.4 and 0.4 mg/l), limit of linearity (9.0 and 9.0 mg/l), enrichment factor (33.48 and 83.71) and percent relative standard deviation (3.44 and 4.20) were found to be for auramine o and crystal violet dyes, respectively. Finally, the method was successfully applied for the preconcentration and determination of AO and CV in water samples and ER% of 89.0‐97.0 and 96.2–98.0% as acceptable range were found to be for AO and CV samples, respectively.     

Kinetics of carbon steel dissolution in ammonium chloride solution containing sodium thiosulfate

The dissolution behavior of carbon steel in ammonium chloride (NH₄Cl) solution containing sodium thiosulfate (Na₂S₂O₃) of various concentrations (0.01 and 0.1 M) was investigated using electrochemical impedance spectroscopy (EIS) and other nonelectrochemical techniques. The weight loss and polarization measurements indicate a significant increase in the NH₄Cl corrosion rate of carbon steel on addition of Na₂S₂O_3. The EIS measurements exhibited two capacitive loops at multiple direct current (dc) potentials for both the concentrations. Electrical equivalent circuit (EEC) and reaction mechanism analysis (RMA) were employed to analyze the impedance data. A four-step mechanism with two intermediate adsorbate species of same charge was proposed to explain the dissolution behavior of carbon steel in the given system. The surface coverage values enumerated that the surface was entirely covered with adsorbed species unlike in the pure NH₄Cl system. Charge transfer resistance and polarization resistance values estimated from RMA parameters indicate the increase in a dissolution rate with dc potential. The surface morphology was inspected via field emission scanning electron microscopy, and the corrosion products including surface state of carbon steel electrode were analyzed using energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy.