采用4.8μm中红外量子级联激光器的痕量一氧化碳气体检测仪

一氧化碳是一种无色、无味、有毒、易燃的危险气体,且低浓度的该气体可以使人中毒、窒息、危及生命。因此研制一种能够检测一氧化碳气体浓度的检测仪意义重大,尤其在环境复杂(湿度和粉尘浓度都很大)的矿井下。本文所述的是一种紧凑型检测仪器,其能够灵敏、快速、连续地监测环境空气中痕量一氧化碳气体浓度。该仪器采用激发波长为4.8μm的中红外量子级联激光器(QCL)和红外碲镉汞探测器的最新半导体技术,结合中红外光程长度为76m的多次反射herriott吸收气室,可以在4s的采样时间内实现40nmol·mol-1气体检测灵敏度。同时,该仪器利用差分吸收光谱检测原理,设计了双光路双通道空间光学结构,消除了电调制光源所带来的不稳定性,有效地提高了仪器浓度检测下限。实验表明,该仪器通过所集成的气体浓度反演算法,能够在无需校准的情况下,可以用于环境监测中的实地痕量气体测量,并且操作人员可以通过替换在不同波长下运行的QCL来测量其他气体。     

INVESTIGATION OF BEHAVIOR OF MODE-Ⅰ INTERFACE CRACK IN PIEZOELECTRIC MATERIALS BY USING SCHMIDT METHOD

The behavior of a Mode-Ⅰ interface crack in piezoelectric materials was investigated under the assumptions that the effect of the crack surface overlapping very near the crack tips was negligible. By use of the Fourier transform, the problem can be solved with the help of two pairs of dual integral equations. To solve the dual integral equations, the jumps of the displacements across the crack surfaces were expanded in a series of Jacobi polynomials. It is found that the stress and the electric displacement singularities of the present interface crack solution are the same as ones of the ordinary crack in homogenous materials. The solution of the present paper can be returned to the exact solution when the upper half plane material is the same as the lower half plane material.     

分子间存在引力实验的改进

“分子引力”实验是初中物理“分子运动论”教学中的一个重要的验证性演示实验.传统的演示实验存在着实验现象不明显,成功率不高,不便于学生观察等缺陷.利用甘油能增加液体膜韧性的特点,利用液体膜拉动吸管运动可以让学生很直观地观察到分子间的引力,降低学生对于微观现象的理解难度.     

海洋工程水下结构检测与清污机器人广义预测控制研究

水下机器人（ROV）的运动具有非线性、多耦合和时变等特点,需要一类数学模型要求低、自适应能力强的非线性控制方法。因此以自主研制的新型的面向海洋工程水下结构检测与清污机器人（MC-ROV）为研究对象,通过水池试验,研究并建立了纵向和艏向动力学模型,最后设计了一种新颖的结合PID控制的约束输入输出的直接广义预测控制算法,对MC-ROV纵向、艏向运动展开研究。仿真结果表明,该算法具有计算量小、震荡低、自适应强等优点,具有良好的控制效果。     

基于DM3730的微小型四旋翼自主着陆视觉系统研究

为实现微小型四旋翼无人飞行器的视觉导引自主着陆过程,采用TI公司DM3730芯片作为核心处理器,构建一套自主着陆视觉导引处理系统。手动飞行实验结果表明,在常规条件下,该系统能够有效识别人工着陆标识,并解算出其与飞行器的相对位置信息用于自主着陆导引。     

DYNAMIC BEHAVIOR OF TWO PARALLEL SYMMETRY CRACKS IN MAGNETO-ELECTRO-ELASTIC COMPOSITES UNDER HARMONIC ANTI-PLANE WAVES

The dynamic behavior of two parallel symmetry cracks in magneto-electro-elastic composites under harmonic anti-plane shear waves is studied by Schmidt method. By using the Fourier transform, the problem can be solved with a pair of dual integral equations in which the unknown variable is the jumps of the displacements across the crack surfaces. To solve the dual integral equations, the jumps of the displacements across the crack surface were expanded in a series of Jacobi polynomials. The relations among the electric filed, the magnetic flux and the stress field were obtained. From the results, it can be obtained that the singular stresses in piezoelectric/piezomagnetic materials carry the same forms as those in a general elastic material for the dynamic anti-plane shear fracture problem. The shielding effect of two parallel cracks was also discussed.     

葡萄糖和Pd对钴基费托合成催化剂结构和性能的影响

采用等体积浸渍法制备SiO_2负载的钴基催化剂,利用N_2低温吸附、XRD、SEM和H_2-TPR等方法表征了在浸渍操作中添加葡萄糖和助剂Pd对催化剂结构和性质的影响,并在固定床反应器中评价了催化剂的费托合成反应性能。葡萄糖和Pd能够改变Co_3O_4晶粒形状,添加葡萄糖提高了Co_3O_4的分散程度,助剂Pd促进了Co_3O_4还原。两者的联合使用则同时提高了钴物种分散度和还原度,从而改善了催化剂的费托合成反应活性和C_(5+)烃选择性。     

石灰乳泡沫法强化脫硫

以便宜易得的石灰乳为脫硫剂。采用泡沫法,在装有五块和三块篩板塔中,对煤气进行了强化脱硫試驗。由試驗結果得出塔板上泡沫的平均高度H以及传貭系数K分別与煤气空塔流速W和石灰乳比用量l(每米~3煤气所用的石灰乳升数)相互关系的数学公式。在一定条件下,脫硫效率可达90％以上,試驗結果还指出脫硫过程中CO_2被吸收的量很小。本法在工业上应用时,如与砷碱法或鉄碱法相比,成本不相上下,但是本法具有基建投資低,鋼材用量少、工艺流程簡单和原料易得等优点,缺点是石灰乳的利用率不高,用过的石灰乳的处理較困难。对于中小型企业的燃料煤气的脫硫以及合成煤气的第一段脱硫,本法值得推广使用。     

Competitive Exclusion Principle Revised by Noise

A fundamental tenet in theoretical ecology is the competitive exclusion principle. Two competitive species for a limited resource cannot coexist and thus one of the species will be driven to extinction. However, we show that noise can revise this principle in a resonance-like manner, which makes coherence resonance in the system. Our obtained results well enrich the findings in the interaction of populations in ecosystems, which may explain some filed observations in the real world.     

偶氮基团引发PMMA在纳米TiO2表面接枝聚合研究

采用表面接枝反应的方法,在纳米TiO2上接枝偶联剂KH-560,进而通过酯化反应引入偶氮基团引发甲基丙烯酸甲酯发生自由基聚合反应,并通过IR、SEM、TEM、DSC和TG等测试方法研究了反应条件对复合粒子结构和性能的影响.结果表明,反应约60 min时,TiO2表面的接枝率达42.9%;当搅拌速率为1.0×104 r/min时,TiO2均匀分散在PMMA基体中;TiO2粒子的加入使得PMMA的热稳定性有了明显提高.