优化自抗扰控制器在船舶主机上的应用与仿真研究

船舶主机速度控制系统具有典型的非线性和不确定性,并受到调速器执行能力的约束及风、浪、流等的干扰,使得主机速度控制器的设计非常困难。给出了带有船舶主机非线性数学模型,将自抗扰控制(ADRC)应用于船舶主机控制,并针对ADRC一些参数不易确定的问题,提出了一种优化目标函数,应用遗传算法对ADRC参数进行优化设计,从而设计出船舶主机优化ADRC控制器。仿真结果表明:该控制器对于船舶主机的非线性、参数不确定性、环境不确定性均有较强的鲁棒性;速度切换控制过程快速、平滑,可以实现高精度的速度控制。     

Poly(maleic acid-co-propane-1,2-diol-co-adipic acid) for pH-triggered drug delivery

Poly(maleic acid-co-propane-1,2-diol-co-adipic acid) was synthesized using xylene as the reaction medium in Dean–Stark apparatus. The synthesized co-polyester was characterized by its FTIR-spectrum, elemental analysis, molecular weights, solubility in common organic solvents and hydrolytic degradation test. From the hydrolytic degradation study it was found that the polyester sample remained almost intact in the acid medium but gradually degraded in basic medium. Because of such pH-responsive degradation nature, this polyester was tried as an enteric coating material for non-steroidal anti-inflammatory drugs. Drug release from the polymer coated specimen in simulated physiological environments was investigated and British Pharmacopoeia standard enteric coating properties of the polymer were observed.     

古建筑榫卯节点抗震加固试验

为探究中国古代大木作结构抗震加固的有效方法,分别采用马口铁和CFRP加固榫卯节点,研究了节点加固前后构架的抗震性能.制作了1:8缩尺比例的木结构空间模型,通过进行低周反复加载试验,获得了构架加固前后的力-侧移曲线,并对比分析了相应的骨架曲线、耗能能力、刚度退化、变形能力等抗震指标.结果表明:马口铁和CFRP均可提高构架...     

基于高斯噪声的孪生近端最小二乘支持向量回归模型研究及应用

孪生近端最小二乘支持向量回归机(twin proximal least squares support vector regression,TPLSSVR)是在PLSSVR模型的理论基础上结合TSVR模型的双超平面理念而设计的一种新的回归模型. 本文利用TPLSSVR模型框架构建了基于高斯噪声的孪生近端最小二乘支持向量回归模型. 该模型利用最小二乘方法,分别加入正则化项b²₁、b²₂,将一个不等式约束问题转化为两个更简单的等式约束问题,提高了模型的泛化能力,有效提升了预测精度. 为解决模型的参数选择问题,选用收敛速度快、鲁棒性好的粒子群优化算法对模型参数进行优化选择. 将新构建的模型应用于人工数据集和风速数据集,实验结果显示该模型有较好的预测效果.     

高铁复杂网络拓扑特征及节点中心性研究

以我国主要代表性城市为研究对象, 分析高速铁路网络特性与拓扑特征, 识别高铁网络中的节点城市及其功能作用。运用Space-P方法构建高铁网络模型, 利用复杂网络理论及Pajek分析软件, 从度值、平均路径长度、聚集系数及节点城市中心性等方面研究我国高铁网络的拓扑结构及节点中心性, 结果表明: 我国高铁网络整体聚集性较高、连通性较强, 东中部及沿海城市表现出高聚集性, 西部城市高铁网络连通性低, 聚集性较弱; 高铁网络具有小世界特征, 任意两节点之间通过较少的中转次数即可连通, 少数城市间需中转三次才能连通; 在高铁网络中, 度值较大的城市主要集中在我国东中部及沿海地区, 西部及东北地区城市度值较小且度中心性较大, 其接近中心性也较大; 而度值较小且介数中心性较大的城市具有较强的中转能力。     

Fatigue limit of new precipitation-hardened aluminium alloy with distinct fatigue crack propagation limit

The goal of this study was to confirm the presence of fatigue limit in a plain specimen of a new precipitation-hardened aluminium alloy. The alloy was fabricated by adding 0.53% excess Mg to the standard 6061-T6 aluminium alloy with a balanced Mg₂Si composition. There were two challenges in this study: verification of the existence of fatigue limit in this new alloy and interpretation of the large scatter in specimen life at the low stress level amplitude. For the former, the existence of a fatigue limit was confirmed by a coaxing effect test. For the latter, the initiation and growth behaviors of a small fatigue crack at low stress amplitude were observed by plastic replica method not only with an optical microscope but also with a scanning electron microscope (SEM). The study results showed that the large scatter in specimen fatigue life at the low stress level amplitude was due to the anomalous initiation and growth behaviors of the small fatigue crack, which in turn was strongly influenced by local conditions. Finally, a conservative S–N curve of this new alloy evaluated by using a plain specimen could be obtained where a distinct knee point showed at cycles of about 10⁶.     

透水水泥稳定碎石排水性能的影响因素分析

通过测试试件7 d无侧限抗压强度、孔隙率、渗透系数等指标,研究了级配、水泥用量、成型工艺等因素对透水水泥稳定碎石排水性能的影响。结果表明,透水水泥稳定碎石采用最大密实级配理论连续开级配设计,最佳级配为:m(5~10 mm碎石)∶m(10~20 mm碎石)=25∶75;水泥的最佳用量为7%;通过静压成型与插捣成型法对形成透水水泥稳定碎石结构较为有利;按最佳级配和水泥用量,采用静压成型,得到的透水水泥稳定碎石7 d无侧限抗压强度为4.7 MPa,孔隙率为15.2%,透水系数为1.54 mm/s。     

可降解聚硅基酯的合成及与苯乙烯的交联反应

采用二元羧酸与二元氯硅烷缩聚制备聚硅基酯的方法,将富马酸二叔丁基酯与1,3-二氯-四甲基二硅氧烷反应合成了黏性液态的不饱和聚(富马酸-四甲基二硅氧烷硅基酯);以偶氮二异丁腈作为引发剂,将该聚硅基酯与苯乙烯进行交联反应,黏性液态的聚硅基酯交联后转变成固态。通过傅里叶变换红外光谱、差示扫描量热法和热重法对聚硅基酯及其与苯乙烯的交联产物进行了分析,结果表明交联后的产物比未交联聚硅基酯的玻璃化转变温度明显升高,热稳定性增强。