超声在固体火箭发动机无损检测中的应用

在固体火箭发动机的研制中，无损检测技术非常重要。本文介绍了一些主要的超声检测方法及其应用。脉冲多次反射法用于检测固体火箭发动机壳体与衬层之间的粘结质量。特性参数和扫频超声法以多层介质理论为基础，用于检测固体火箭发动机的深层粘结质量。     

非醚合氢化铝的制备及性质研究

本文论述了大晶粒α-AlH_3的合成条件,从而制得高纯度产品;对α-AlH_3和α′-AlH_3的稳定性进行比较研究表明,α′-AlH_3也是一种相当稳定的非醚合氢化铝;提出了α-AlH_3与α′-AlH_3的分离方法。     

瞬时气压记忆型水箭的制作

利用塑料饮料瓶，胶塞，自行车气嘴及一次性注射器等材料制作一个装置，实现了水箭发射瞬时的内气压记忆，为安全发射和定量研究变质量问题提供一简便的实验演示。     

Laminar-turbulent transition in the boundary layer on cones in a hypersonic flow at high Reynolds numbers per meter

The laminar-turbulent transition is experimentally studied in boundary-layer flows on cones with a rectangular axisymmetric step in the base part of the cone and without the step. The experiments are performed in an A-1 two-step piston-driven gas-dynamic facility with adiabatic compression of the working gas with Mach numbers at the nozzle exit M _∞ = 12–14 and pressures in the settling chamber P₀ = 60–600 MPa. These values of parameters allow obtaining Reynolds numbers per meter near the cone surface equal to Re _1e = (53–200) · 10⁶ m ⁻¹. The transition occurs at Reynolds numbers Re _tr = (2.3–5.7) · 10⁶. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 3, pp. 76–83, May–June, 2007.     

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A simple, robust, and accurate HLLC-type Riemann solver for the compressible Euler equations at various Mach numbers is built. To cure shock instability of the HLLC solver at strong shocks, a pressure-control technique, which plays a role in limiting the propagation of erroneous pressure perturbation, is proposed. With an all Mach correction method for the compressible Euler system, the proposed method is further extended to compute flow problems at low Mach numbers. The proposed all Mach HLLC-type scheme has been implemented and used to compute a variety of flow problems ranging from hypersonic compressible to low Mach incompressible flow regimes. Various numerical results demonstrate that the obtained all Mach HLLC-type scheme is both accurate and stable for all speed ranges.     

离子色谱法在氢燃料电池汽车用氢气中的应用现状及展望

氢燃料电池汽车用氢气中痕量杂质会影响氢燃料电池的性能,国内外标准均严格规定了痕量杂质的限值要求。离子色谱法（IC） 具有操作简单、分析快速、灵敏度高、选择性好、可多组分检测的特点,ISO 14687－2∶2012、SAE J2719∶2015和GB/T 37244－2018等标准均涉及到离子色谱法分析其中的部分指标。目前离子色谱法在环境空气、固定污染源废气、天然气、烟气等气体分析领域有广泛应用,在氢燃料杂质的分析领域尚在起步阶段。该文综述了氢燃料和其他气体分析领域中总卤化物、甲酸、氨和总硫化物的分析方法,将离子色谱与不同分析技术进行比较。并基于离子色谱在其他气体杂质分析领域的应用进展,对其在氢燃料电池汽车用氢气杂质分析中的应用作出展望。     

无人飞行器视觉SLAM特征检测和匹配算法研究

近几年图像局部特征检测和描述在机器人视觉中得到了广泛的应用,鲁棒的、快速且高精度的视觉特征检测和描述算法对飞行器进行实时的位姿估计和地图构建具有决定性意义。本文针对四旋翼无人飞行器平台的RGB-D传感器同时定位与地图构建(SLAM),讨论FAST、STAR、SIFT和SURF等检测算法和ORB、FREAK和SURF等匹配描述符的性能,对不同的特征算法进行对比评估出最合适的特征检测方法和匹配描述符。最后,基于Eclipse与OpenCV平台进行了实验,实验结果表明FAST检测和FREAK描述符比其他方法更适用于四旋翼飞行器在板视觉SLAM,且能基本满足实时性。     

Artificial ageing of double base rocket propellant

The ageing of double base rocket propellants (DB rocket propellants), which is a consequence of chemical reactions and physical processes that take place over time, has significant effect on their relevant properties (e.g. chemical composition, mechanical properties, ballistic properties, etc.). The changes of relevant properties limit the safe and reliable service life of DB rocket propellants. This is the reason why numerous research efforts are devoted to finding out reliable methods to measure the changes caused by ageing, to assess the quality at a given moment of time, and to predict remaining life-time of DB rocket propellants. In this work we studied dynamic mechanical properties of DB rocket propellant artificially aged at elevated temperatures, in order to detect and quantify changes in dynamic mechanical properties caused by the ageing. Dynamic mechanical properties were studied using dynamic mechanical analyser (DMA). The results obtained have shown that the ageing causes significant changes of DMA curve’s shape and positions. These changes are quantified by following some characteristic points on DMA curves (e.g. glass transition temperatures; storage modulus, loss modulus and tanδ at characteristic temperatures, etc.). It has been found out that the most sensitive parameters to the ageing process are: storage modulus at viscoelastic and softening region, peak width and height on loss modulus curve, glass transition and softening temperature, and tanδ at viscoelastic region.