基于温度-应力试验的自生体积变形计算起点的研究

针对标准试验方法在混凝土自生体积变形计算起点方面尚存在的问题,本文以微膨胀抗冲磨混凝土为研究对象,对ASTM C1074活化能测试方法进行改进,获得更为准确的胶凝材料水化反应活化能,并基于活化能计算得到实际温度条件下试件的等效龄期;利用温度-应力试验的特点,以第一零应力对应的等效龄期作为自生体积变形的有效计算起点,在日本混凝土学会提出的混凝土自生体积变形模型基础上,以自生体积变形最大膨胀值作为分界点分段模拟分界点前后的变形,建立以温度-应力试验第一零应力时间为计算起点的自生体积变形模型,为准确建立抗裂机理模型提供参考依据。     

Dependence of oil stability index of fatty compounds on their structure and concentration and presence of metals

During storage and use, vegetable oil-derived industrial products such as biodiesel and biodegradable lubricants can be subjected to conditions that promote oxidation of their unsaturated components. The materials arising during oxidation and subsequent degradation can seriously impair the quality and performance of such products. Therefore, oxidative stability is a significant issue facing these vegetable oil-derived products, and enhanced understanding of the influence of various components of vegetable oils and storage parameters is necessary. In this work, the oil stability index (OSI) was used for assessing oxidation of monoalkyl esters of FA by varying several parameters. Neat fatty compounds and prepared mixtures thereof were studied for assessing the influence of compound structure and concentration. Small amounts of more highly unsaturated compounds had a disproportionately strong effect on oxidative stability. The recently developed concept of bis-allylic equivalents correlated more closely than the iodine value with the OSI times of mixtures of fatty esters. The OSI times of free acids were shorter than those of the corresponding alkyl esters. The presence of copper, iron, and nickel also reduced oxidative stability, but their effect was less than the presence of more highly unsaturated fatty compounds. Of these metals, copper had the strongest catalytic effect on OSI time. OSI may be an alternative to long-term storage tests for determining the influence of extraneous materials such as metals on oxidative stability.     

基于浮点型编码策略的差分多目标柔性车间调度优化

运用进化算法求解柔性车间调度问题时,编码的特殊性对进化策略造成的局限制约了算法的搜索能力。为此,提出一种基于浮点型编码策略的差分多目标优化算法。该算法采用基于工序权重的浮点数编码—解码机制,消除了排列组合型编码方式对进化操作带来的约束,运用差分进化策略生成新个体,以提高优秀个体产生的几率,进而保证算法有更好的收敛性。将算法与传统算法及其改进形式在相同测试用例上进行对比,结果表明,本算法在保证收敛性的同时,搜索到更多的非支配个体,体现出更好的分布性。此外,提出了平行决策和等价平行决策的定义,将柔性车间调度模型的研究拓展至决策空间。     

瓷质砖湿坯对流干燥过程的传热传质研究

引用建立于Whitaker的体积平均方程和Darcy定律基础止的多孔介质内部热质传递的等效耦合扩散模型，寻出一组关于液体饱和度、温度和气相压力的新支配方程，应用该方程组对瓷质砖坯体干燥过程进行了数值分析和实验测定。在平均含湿饱和度的变化方面，数值解与实验结果十分吻合。还改变影响坯体干燥过程的一些因素进行计算机模拟计算，通过改变这些因素的大小来考察计算结果，以期获得某些定性或定量的结论，从而用以指导实际生产过程。     

Dynamic equivalent method of interconnected power systems with consideration of motor loads

The existing equivalent methods usually only deal with static load models and neglect the dynamic characteristics of loads such as induction motors.This paper presents a dynamic equivalent method which considers motor dynamics.At first,the clustering criterion of motor loads is given.The motors with similar dynamic characteristics are classified into one group.Then,reduction of motors in the same group is carried out.Finally,parameters of the equivalent motor are calculated and the equivalent system is thus...     

屋顶绿化节能热工评价

研究了屋顶绿化的节能热工评价方法,通过室内环境为空调控制和自然室温2种状态下的屋顶绿化节能热工对比测试,得到主要结果：在夏季空调期间,绿化屋顶热流减少70%左右,附加当量热阻为1.0 m^2.k/w;自然室温环境下绿化屋顶热流方向与对比屋顶相反,绿化屋顶的冷却效率为111%。     

基于Blowfish和MD5的混合加密方案*

针对Blowfish算法在实际应用中存在的等价密钥、重复初始化等问题,提出Blowfish与MD5算法相结合,将MD5算法的生成值作为密钥的一部分对Blowfish算法进行初始化,使用概率统计方法证明该方案弥补了Blowfish算法的实际应用缺陷。计算结果表明,混合加密方案具有更高的安全性、更快的速度。     

电力系统备用容量模型

发电设备合理备用容量和备用率问题是电力系统中的一个特殊问题。本文在等效持续负荷曲线概念的基础上,利用曲线拟合的思想,得出了负荷与时间的函数关系式,进一步求得合理备用容量和备用率。     

A force control high-order single-step-β method (HSM) for substructure pseudo-dynamic testing

This paper proposes a new technique which introduces the high-order single-step-β method(HSM)into the experimental study on the substructure pseudo-dynamic testing(SPDT).The technique is based on the proposed concept of equivalent shear stiffness which can meet the requirement of the HSM algorithm.A study is done to theoretically validate the technique by the numerical analysis of two-storey shear building structure,in comparison of the proposed substructure pseudo-dynamic testing algorithm with the central difference method(CDM).Then,a full-scale SPDT model,the three-storey frame-supported reinforced concrete short-limb masonry shear wall structure,is designed and tested to simulate the seismic response of the corresponding six-storey structure and verify the proposed force control HSM technique.Meanwhile,the techniques of both stiffness correction and force control are suggested to control algorithmic error,control error and measurement error.The results indicate that the force control HSM can be used in the full-scale multi-degree-of-freedom(MDOF)substructure pseudo-dynamic testing before descent segment of structure restoring force properties.     

大涡模拟-Lighthill等效声源法的空腔水动噪声预测

为了考察空腔产生的水动噪声,对气动声学理论与研究方法进行了分析,确立了大涡模拟-等效声源混合法.利用大涡模拟计算空腔非定常流动的流场结构,基于有限元/无限元法利用变分形式的Lighthill声类比方程进行声场的求解.利用该混合法考察了雷诺数为1.2×105的空腔算例频域内噪声的辐射特性,基频值的预测结果与文献基本一致,低频纯音的远场辐射具备指向性,沿上游方向辐射能量较高,高频宽带噪音的传播不具指向性.