Experimental study on inhibition of low pressure premixed flat methane-oxygen flames by trifluoromethane

This paper presents measurements of combustion species of low pressure laminar premixed flat methane-oxygen flames inhibited by triflnoromethane （CF3H） using synchrotron radiation-molecular beam mass spectrometry （SR-MBMS）. Fire suppression chemistry of CF3H is investigated by selective detection of combustion radicals and intermediates. Results show that SR-MBMS offers a powerful tool for studying fire suppression chemistry of halon replacements, which may extensively detect combustion species in the inhibited flames, especially radicals and intermediates. The suppressant CF3H is completely consumed in the preheat zone of premixed flames and produces fluorinated radicals such as CF3 and CF2. CF3 is the main radical participating in flame inhibition cycles in the reactive zone.Unlike HBr, HF produced by CF3H is very stable and will not act as a radical scavenger because the bond energy of H-F is much higher than that of H-Br, which is responsible for less effectiveness than conventional bromine-based suppressants.     

Optimization of polymer electrolytes for quasi-solidstate dye-sensitized solar cells

The dye-sensitized nanocrystalline TiO2 thin filmsolar cells (DSSCs) have attracted much attention since1990s[1— , due to their high light to electrical energy 4]conversion efficiency. So far, many studies have beenmade on the use of liquid electrolytes such as acetonitrile,3-methoxypropionitrile and a mixture of ethylene/pro-pylene carbonate (EC/PC) containing I? /I3 redox cou-?ple. A light to electrical energy conversion efficiency of7%— 12% has been obtained for DSSC using liquid e…     

Basal tyrannosauroids from China and evidence for protofeathers in tyrannosauroids

Tyrannosauroids are one of the last and the most successful large-bodied predatory dinosaur groups, but their early history remains poorly understood. Here we report a new basal tyrannosauroid from the Early Cretaceous Yixian Formation of western Liaoning, China, which is small and gracile and has relatively long arms with three-fingered hands. The new taxon is the earliest known unquestionable tyrannosauroid found so far. It shows a mosaic of characters, including a derived cranial structure resembling that of derived tyrannosauroids and a primitive postcranial skeleton similar to basal coelurosaurians. One of the specimens also preserves a filamentous integumentary covering similar to that of other coelurosaurian theropods from western Liaoning. This provides the first direct fossil evidence that tyrannosauroids had protofeathers.     

光路系统分析法及在法布里─泊罗干涉仪中的应用

以琼斯矩阵和系统理论为基础．提出了一种光路系统分析法．它适用于描述光波矢量、光功率和线性光器件输入输出的静态传递函数．应用该方法建立了光纤法布里─泊罗干涉仪的数学模型．所得结果表明．该方法优于其它方法．从而验证了本方法的正确性和实用性．     

发展力量素质与掌握体操技术关系的探讨

本文采用调查和统计分析的方法,发现体育系学生的体操技术成绩与上肢的推撑力量、腹肌力量有中度正相关关系。     

Four-winged dinosaurs from China

Although the dinosaurian hypothesis of bird origins is widely accepted, debate remains about how the ancestor of birds first learned to fly. Here we provide new evidence suggesting that basal dromaeosaurid dinosaurs were four-winged animals and probably could glide, representing an intermediate stage towards the active, flapping-flight stage. The new discovery conforms to the predictions of early hypotheses that proavians passed through a tetrapteryx stage.     

UWB雷达信号设计方法研究

本文首先讨论了高斯白噪声环境下超宽带（ＵＷＢ）雷达信号设计问题，提出了一种自适应最优波形设计方法。这种方法可以集中目标散射回波能量，从而大大提高了接收信号的信噪比；其次，对杂波干扰下的低能量相干目标环境，根据牛曼—皮尔逊准则提出了一种非线性方程牛顿迭代法，与现有的ＵＷＢ信号方法相比，信噪比要改善１０ｄＢ左右。     

天线阵与馈电网络不匹配对低副瓣天线性能的影响

本文利用网络理论分析了天线阵与馈电网络的相互作用,给出了分析计算公式,并以32元共轴振子线阵为例,计算了方向图变化的情形。由分析公式和计算结果可以看出,为了获得低副瓣方向图,必须严格控制功分器网络的精度及使天线阵与馈线有良好匹配。     

利用共轭梯度法分析有限矩形波导相控阵

对于大阵一般把它作为无限阵来分析,求得其输入阻抗和其它参数。无限阵可以用周期结构进行严格求解,因为采用周期结构,实际上只要求解一个单元室就可以,这样问题相对来说就简单多了。但对于小阵采用无限周期结构误差较大,因此必须采用有限阵的分析方法。有限阵分析方法常常因为问题太复杂,受计算机容量和速度的限制,只能求解较小的阵。为此本文介绍了一种带有无限接地板的有限阵分析方法,这种方法是采用模匹配法严格地求解边值问题,因此求解精度比较高。另外,本文在公式推导、简化以及计算方法上采取了以下措施,即在求解过程中,本文利用列文的方法,将四重积分化为二重积分,计算量可大大减少。同时,本文还利用Toeplitz性质,将计算量进一步减少。Toeplitz性质和共轭梯度法的结合,将储存空间大大减少,使得对较大的有限阵分析成为可能,这使得本方法在工程实际中具有更大的使用价值。