考虑共因失效和负载分担的表决系统维修优化分析

随着仪器设备的大型化、精密型和复杂化，传统的单一故障模型很难精确地描述系统。针对可修的表决系统，考虑了负载分担和共因失效两种失效模式，提出了不完美的故障检测策略，并对模型进行了可靠性和维修性分析，求得了系统的瞬时可用度、稳态可用度和平均维修费用。最后通过数值案例给出了同时考虑可用度和维修费用的最优检测策略，能够为设备管理者提供决策依据。     

基于新型神经网络的乐曲内容检索技术研究

基于文字符号的检索体系,对于音乐材料效果不佳,基于内容的音乐信息检索会成为今后发展的关键。针对音乐检索技术的核心——音频特征描述和特征匹配,本文以音高和相对节奏为音乐作品的关键特征,发展了非毗邻层连接的前馈神经网络结构,给出了误差反传训练算法的分类器,并进行了试验研究。结果表明,非毗邻层连接的前馈神经网络结构有优越的识别性能和极快的收敛速度。     

基于动基座自动调平控制策略研究

自动调平控制技术是为了解决动基座上的搜跟系统360°全域周扫过程中,俯仰与大地水平角度实时保持的问题。该系统是在速率闭环稳定的基础上,采用倾角传感器构成空间位置环,形成位置与速率双闭环,实现系统瞄准线的自动调平。针对平台控制的关键?自动调平技术,着重分析了倾角传感器与平台万向架角度构成的空间位置环,理论推导出搜跟系统的瞄准线与水平面夹角的关系,并进行系统控制分析和仿真。最终仿真分析结果与实际测试结果基本吻合,满足系统的指标要求。     

飞秒激光烧蚀固体靶的冲击压强

在明确飞秒激光与物质相互作用过程中冲击压强和冲击温度概念的基础上, 讨论了飞秒激光烧蚀铝、铜、硅三种固体靶过程中的冲击压强与其他物理量的关系, 利用飞秒激光烧蚀固体靶的时间分辨泵浦探测阴影图提取了冲击压强的绝对值. 此项研究结果对飞秒激光安全加工含能材料以及飞秒激光推进技术有重要意义. 关键词： 飞秒激光 含能材料 冲击压强 冲击温度     

飞秒激光烧蚀金属靶的冲击温度

在明确飞秒激光与物质相互作用过程冲击温度概念的基础上, 讨论了飞秒激光烧蚀铝靶和铜靶过程中的冲击温度与其他物理量的关系, 利用飞秒激光烧蚀金属的双温模型提取了冲击温度的绝对值, 基于非傅里叶热传导模型计算了冲击温度的分布. 此项研究结果对飞秒激光安全加工含能材料有借鉴意义. 关键词： 飞秒激光 含能材料 烧蚀 冲击温度     

Femtosecond laser ablation of silicon in air and vacuum

Femtosecond(fs) pulse laser ablation of silicon targets in air and in vacuum is investigated using a timeresolved shadowgraphic method. The observed dynamic process of the fs laser ablation of silicon in air is significantly different from that in vacuum. Similar to the ablation of metallic targets,while the shock wave front and a series of nearly concentric and semicircular stripes,as well as the contact front,are clearly identifiable in the process of ablation under 1×10 5 Pa,these phenomena are no longer observed when the ablation takes place in vacuum. Although the ambient air around the target strongly affects the evolution of the ablation plume,the three rounds of material ejection clearly observed in the shadowgraphs of fs laser ablation in standard air can also be distinguished in the process of ablation in vacuum. It is proven that the three rounds of material ejection are caused by different ablation mechanisms.     

A simulation study of water property changes using geometrical alteration in SPC/E

We present a systematic investigation of the impact of changing the geometry structure of the SPC/E water model by performing a series of molecular dynamic simulations at 1 bar(1 bar = 105 Pa) and 298.15 K. The geometric modification includes altering the H–O–H angle range from 90° to 115° and modifying the O–H length range from 0.90 A to 1.10 A in the SPC/E model. The former is achieved by keeping the dipole moment constant by modifying the O–H length, while in the latter only the O–H length is changed. With the larger bond length and angle, we find that the liquid shows a strong quadrupole interaction and high tetrahedral structure order parameter, resulting in the enhancement of the network structure of the liquid. When the bond length or angle is reduced, the hydrogen bond lifetime and self-diffusion constant decrease due to the weakening of the intermolecular interaction. We find that modifying the water molecular bond length leading to the variation of the intermolecular interaction strength is more intensive than changing the bond angle. Through calculating the average reduced density gradient and thermal fluctuation index, it is found that the scope of vd W interaction with neighbouring water molecules is inversely proportional to the change of the bond length and angle. The effect is mainly due to a significant change of the hydrogen bond network. To study the effect of water models as a solvent whose geometry has been modified, the solutions of ions in different solvent environments are examined by introducing NaCl. During the dissolving process, NaCl ions are ideally dissolved in SPC/E water and bond with natural water more easily than with other solvent models.     

Cε3-Cε4蛋白寡核苷酸适配子结合位点的预测与筛选

采用NPDock程序对Cε3-Cε4蛋白与其核酸适配子A1的结合位点进行了预测与筛选, 筛选出A1与Cε3-Cε4蛋白结合的关键位点. 同时, 根据蛋白与DNA片段复合物结合界面中氨基酸残基和碱基统计分析发现, 结合界面氨基酸富集碱基G能力最强, 富集碱基T和C能力次之. 本文建立了以NPDock程序虚拟对接为基础的高效适配子优化方法, 为相关研究提供了实验参考.     

橡胶硫化促进剂3-甲基-2-噻唑硫酮制备及光谱分析

采用一步法合成出了3-甲基-2-噻唑硫酮(MTT),通过FTIR,XRD,TG-DSC对其进行检测和表征,揭示了MTT的微观结构和内在规律性。FTIR揭示了MTT分子内部的各元素之间的化学键键型,XRD从晶胞参数、晶面指数等晶体学数据,变换出MTT晶体微观结构,完成了MTT物相组成和结构的定性鉴定。TG-DSC检测出了MTT的质量变化与热效应两种信息,MTT的相变和分解温度分别为76.3和306.9 ℃,MTT的分解温度偏高,为采用硫化仪研究MTT的橡胶硫化性能提供参考。本研究为企业选定工作标准品,对MTT工业化生产进行跟踪检测,评判MTT的产品性能指标,提供基础实验数据。     

不同土壤栽培对细叶小羽藓(Haplocladium microphyllum)生长发育的影响

苔藓植物的园艺园林应用日益受到重视,细叶小羽藓(Haplocladium microphyllum)是一种交织生长、色泽翠绿、越冬能力强、观赏价值较高的林地野生苔藓资源.以黄泥土、黄砂土、白泥土为基质在光照培养箱内对细叶小羽藓进行栽培,利用盖度、分枝长度、分枝数、生物量、相对含水量及光合色素质量比等指标评价了细叶小羽藓生长发育状况,探讨了不同土壤类型对细叶小羽藓生长发育的影响.试验表明,黄泥土栽培细叶小羽藓生长效果最佳,栽培50d其盖度可达84.33%,分枝长度为4.80cm,一级及二级分枝数为11.87和5.13个,鲜重及干重分别增长38.15和17.69倍,黄砂土栽培细叶小羽藓生长效果次之,白泥土最差;不同土壤栽培细叶小羽藓光合色素质量比依次为黄泥土>黄砂土>白泥土,其中黄砂土栽培与野外生长光合色素质量比最相近;培养箱中用不同土壤栽培细叶小羽藓不改变其耐阴性.