可调谐二极管激光吸收光谱诊断燃烧参数

近红外二极管激光吸收光谱诊断技术以其高灵敏,响应快,结构相对简单,造价低廉等优点已成为测量准均匀燃烧场和流动场温度和组分分压的有效手段.本文介绍我们所建立的可调谐二极管激光吸收光谱诊断系统以及利用此系统进行燃烧产物H_2O浓度和温度的实验结果.作者还介绍了所发展的高敏感的探测技术-波长调制光谱(WMS,Wavelength Modulation Spectroscopy)的2f诊断技术.可调谐二极管激光吸收光谱技术可望应用于动态燃烧过程的诊断与控制.     

Core reinforcement design for improving flexural energy-absorption of corrugated sandwich composite structure

To strengthen Specific Energy-Absorption (SEA) behavior of Sandwich Composite Structure (SCS), a kind of light-weight vertical stiffener is proposed for the corrugated core. The vertical stiffener, embedded in the corrugated core, can not only absorb part of energy but also simultaneously enhance Energy-Absorption (EA) of other components. The Hashin damage model considering the shear stress and ductile damage model is adopted to predict the failure of carbon fiber face-sheets and aluminum-core, respectively. The perfect bonding is modeled for interfaces between the face-sheet and core due to little realistic debonding. The finite element model is verified by available data of conventional SCS. To obtain more design ideas, several stiffeners with different thicknesses, numbers, and positions are investigated. From the predicted results, both the flexural load and deformation of SCS correlate well with experimental results. It is highlighted that the SCSs with different vertical stiffeners exhibit 9.74%–58.48% higher SEA than the SCS without stiffener. The complex reinforcement mechanisms are extensively revealed by underlying coupling EA and deformation mechanisms. Structural parameter analysis shows that the thickness and number have significant effects on the flexural behavior and SEA of reinforced SCS.     

Response of photosynthetic systems to salinity stress in the desert cyanobacterium Scytonema javanicum

The present study investigated the physiological and biochemical characteristics of Scytonema javanicum, a pioneer species isolated from desert biological crusts, under salinity stress. Pigment analysis showed that salinity decreased chlorophyll a and phycocyanin content, while low salinity increased carotenoid concentration and high salinity decreased carotenoid concentration. Salinity also inhibited CO₂ assimilation rate and photosynthetic oxygen evolution in this cyanobacterium. Chlorophyll a fluorescence transient parameters (φPo, φEo, ψO, RC/ABS, RC/CS, PI_ABS, and PI_CS) were decreased under salt stress, while dVo/dto(Mo), Vj and φDo were increased. The decrease of ETRmax and Yield and the change of chlorophyll a fluorescence transients showed that salt stress had an important influence on photosynthesis. These results indicated that the effects of salinity stress on photosynthesis in S. javanicum may depend on the inhibition of electron transport and the inactivation of the reaction centers, but this inhibition may occur in the electron transport pathway at the PSII donor and acceptor sites.     

纤维增强树脂基复合材料的吸湿性和湿变形

阐述了纤维增强树脂基复合材料的吸湿与湿变形机理及其影响因素,从环境、材料和工艺3个方面,总结了环境温度、相对湿度、纤维、树脂基体、纤维-基体界面以及铺层方式对复合材料吸湿性与湿变形的影响,并提出了降低纤维增强树脂基复合材料吸湿率与湿变形的途径。     

M-型皱褶芯材夹层板吸能性能研究

作为先进复合材料夹层结构,皱褶夹层板是一种具有众多优点的新型夹层板结构。本文建立了带有缺陷的皱褶芯材有限元模型,对M-型皱褶芯材的能量吸收率和几何参数之间的关系进行了研究。压缩试验仿真结果与CELPACT项目中的试验结果相符。与蜂窝芯材相比,皱褶芯材在吸能性能上表现出了很大的优势,其能量吸收率是蜂窝芯材的两倍多。此外,本文采用响应面法获得了M-型皱褶芯材几何参数和吸能性能指标之间的关系。最后,以吸能性能最优为目标,采用拉丁超立方抽样(LHS)方法获得初始样本,以多目标非支配排序遗传算法(NSGA-Ⅱ)对皱褶芯材进行了优化。     

利用单色装置的部分偏振化测定二向色性研究

介绍了测量红外二向色性的一种新方法，利用单色装置的部分偏振化测定二向色性。根据双光路红外分光光度计的结构特点以及红外吸收规律，文中论述了利用单色装置的部分偏振化测定二向色性的可能性，并从红外二向色性原理和马吕斯定律出发，导出了用部分偏振光测定二向色性时透射率之间的关系式，与实验结果符合得很好。     

多胞金属管受径向冲击时的吸能特性

针对某武器装备发射环节对能量吸收提出的要求,并结合当前薄壁金属管件的研究背景以及能量吸收的性能指标,分析了多细胞管件在受径向冲击时的吸能特性。结合实际工况,制定了传统多胞管和夹层多胞管两方面共5种方案,并运用ANSYS/LS-DYNA程序,对其进行逐一建模仿真。最后的结论分析显示,在工艺允许的情况下,夹层多胞管的4板Ⅰ向方案在能量吸收特性方面表现更加优越。     

基于波长调制谐波信号主峰拟合的气体浓度测量方法

为了提高激光波长调制光谱法(WMS)测量气体浓度的速度和准确度,首次提出了一种通过对吸收光谱谐波信号的主峰进行拟合的气体浓度测量方法。在该方法中,只扫描吸收光谱谐波信号的主峰部分来获得谐波信号(WMS-2f/1f)的峰值点。因为缩减了吸收光谱的扫描范围,所以扫描速度得到了提高。通过对吸收光谱谐波信号(WMS-2f/1f)的主峰部分进行多项式拟合,进一步提高了测量精度。详细讨论了多项式阶数的确认方法,以及拟合数据长度对测量结果的影响。通过测量不同情况下的二氧化碳浓度验证了该方法的有效性。     

高温雷达吸波涂层研究进展

在现代信息化战争中,探测和制导技术迅猛发展。在众多探测信号中,雷达探测占比高达60%,因此武器装备雷达隐身 能力尤其重要。随着新一代装备性能的提升,热端部件的服役温度不断升高,对高温雷达吸波涂层提出了更加严苛的要求。在高 温服役环境下,部分雷达吸波材料存在氧化、居里温度低而失去吸波性能的问题。高温雷达吸波材料主要依靠介电损耗和电导损 耗机制实现对电磁波的损耗吸收。基于此,综述了以碳化物、硼化物、氧化物、金属材料、MAX相材料为吸波剂的高温雷达吸波涂 层研究情况,分析了各材料的优势及存在的问题,其中氧化物吸波剂高温稳定性好,易于制备,成本低,其吸波性能可通过掺杂改 性调控,是面向未来更加严苛服役环境下更具应用潜力的吸波材料。此外,还从梯度结构和超材料设计2个角度分析了涂层结构 设计在拓宽涂层吸波频带,降低涂层厚度方面的作用。结合当前研究进展提出了新材料研发、新结构设计和与材料结构相适应的 制备工艺研究是未来高温雷达吸波涂层的发展方向。