APPLICATION OF THE POSITRON ANNIHILATION TECHNIQUE

The principles of positron annihilation and four positron experimental techniques are described. The application of positron annihilation technique in material science. atomic physics and other related fields are discussed.     

Functionalization of multi-walled carbon nanotubes grafted with self-generated functional groups and their polyamide 6 composites

Fourier transform infrared spectroscopy, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy were applied in this study to demonstrate that multi-walled carbon nanotubes synthesized from ethanol flames (F-MWCNTs) inherently have functional groups on their surfaces. This finding clearly indicates that the covalent functionalization of carbon nanotubes can be achieved without oxidation as pretreatment. Thus, n-hexadecylamine functionalized F-MWCNTs (H-MWCNTs) can be synthesized simply, without disrupting the primary structures of the nanotubes. The melt-compounding method was used to fabricate polyamide 6/MWCNTs composites. Scanning electron microscope results confirmed that both F-MWCNTs and H-MWCNTs have much better nanoscopic dispersion in PA6 matrix than commercial MWCNTs, and the tensile strength, Young’s modulus, dynamic mechanical properties, and thermal behavior of their PA6 composites are considerably improved.     

CNG加气母站建设期间应注意的问题与解决方法

总结加气母站在规划、建设与试运行阶段需要注意的问题,针对问题提出一些建议及解决方法,对加气母站的建设具有一定的参考价值。     

Two-stage Combinatory Planning Method for Efficient Wind Power Integration in Smart Distribution Systems Considering Uncertainties

—A crucial factor that may hinder the usage of renewable energies is the mismatch to load demand in the temporal dimension. In the smart-grid environment, demand response is regarded as a feasible solution to mitigate such a problem. In this study, a combinatory planning method is proposed for efficient integration of wind generation. The problem is formulated as a two-stage fuzzy chance-constrained programming model, which co-optimizes the installation of distributed wind generation along with network transformation and determination of optimal real-time prices to achieve the minimization of the total cost over planning horizons. The impact of both aleatory and epistemic uncertainties associated with wind generation, load growth, and responsive behaviors of customers has been considered. Results of the case study demonstrate the effectiveness of the proposed method and the necessity of considering different uncertainties in the planning.     

基于截止期错失率可预测的高利用率容错调度

现代导航与通信等实时系统经常面临着复杂的实时数字信号处理及信息交互需求,处理器处于高利用率状态.对于此类高利用率实时系统,传统的时间冗余容错通常会引发多个任务连续错失截止期的灾难性后果.针对高利用率情况,提出一种截止期错失率可预测的容错调度方法,截止期错失次数不大于出现错误的次数,消除了多个任务截止期连续错失的多米诺效应.进一步地在该方法中融合时间冗余方法的优点,提出了求解检测点上界位置的离线快速算法,有效地降低了截止期错失率.仿真实验表明,与目前已知的同类方法相比,该方法具有更低的截止期错失率.     

基于REDIM方法构建的亚网格燃烧模型及其应用

将近年发展的详细反应机理简化方法:反应-扩散流形(REDIM)方法与假定滤波密度函数相结合,构造了新的亚网格燃烧模型。由于REDIM方法既能描述快速反应状态又能描述扩散过程起主导作用的慢速反应状态,因此新构造的燃烧模型理论上可用于计算扩散和化学反应均起重要作用的湍流部分预混燃烧及分层燃烧模式。为了验证其性能,利用新模型对基准的Darmstadt湍流分层火焰燃烧器进行了大涡模拟(LES)计算:首先分别采用粗、细两种网格对无反应湍流状态进行了计算,以检验网格精度;随后对一个有分层效应的湍流燃烧状态进行了计算。LES计算得到的速度、温度、组分等统计信息与实验结果吻合良好,验证了新亚网格燃烧模型在预测湍流分层火焰方面的能力。     

谐振式硅微结构压力传感器非线性振动特性研究

本文研究了谐振式硅微结构压力传感器在单频激励和双频激励情况下的非线性振动特性。利用多尺度法研究运动方程中三次非线性项对传感器频率特性的影响规律，提出了改善谐振式硅微结构传感器特性的方法以及在实现闭环自激系统时应采取的措施。     

铁皮石斛叶多糖对秀丽隐杆线虫体内抗衰老作用

目的：基于模式生物秀丽隐杆线虫（以下简称线虫）探究铁皮石斛叶多糖的抗衰老能力。方法：采用含不同质量浓度（0.5、1.0、2.0 mg/mL）铁皮石斛叶多糖的大肠埃希氏菌OP50菌液每天饲喂线虫,以饲喂大肠埃希氏菌OP50菌液组作为空白对照,观察铁皮石斛叶多糖对线虫寿命、生殖能力、运动能力和应激能力的影响,同时测定线虫体内活性氧水平及抗氧化酶的酶活力,分析铁皮石斛叶多糖对线虫体内抗氧化能力的影响。结果：与空白对照组线虫相比,在本实验考察的质量浓度范围内,铁皮石斛叶多糖均可延长线虫的寿命,提高其运动、应激能力,同时不会损害线虫的生殖能力,并且能有效提高过氧化氢酶和超氧化物歧化酶的活力,显著降低线虫体内丙二醛含量（P＜0.05）。结论：铁皮石斛叶多糖可能通过提高线虫抗氧化酶活力及提高线虫抗应激能力,降低线虫体内活性氧水平并减缓细胞氧化损伤,进而发挥延长线虫寿命的功效。     

低热通量下碳纤维/环氧树脂层合板的燃烧特性

使用锥形量热仪研究了35 kW/m²热通量下碳纤维/环氧树脂层合板的点燃时间、质量损失速率、热释放速率等燃烧特性参数与其厚度的关系,建立了热穿透深度的数学模型以得到不同厚度层合板的热穿透深度、判别层合板的热厚热薄特性并分析燃烧过程。结果表明：在低热通量下,随着碳纤维/环氧树脂层合板厚度的增加其点燃时间延长、平均质量损失速率和质量损失速率峰值下降、总释放热量增大、热释放速率峰值先增大后减小;碳纤维/环氧树脂层合板在点燃时表现为热薄型或是热厚型,与其物理厚度有直接关系。热厚型材料有一个由热厚型向热薄型转变的热响应过程。     

基于滑移场理论的边坡角优化设计

以临界滑移场理论为基础,采用智能匹配优化设计对布沼坝露天矿到界边坡进行了优化设计技术,得出了到界边坡的最佳坡角,修正原设计中的不足。