基于Flash CS3的B737飞机起落架刹车系统模拟仿真

起落架刹车系统能在飞机着陆时配合扰流板与反推装置增大飞机的阻力,使之迅速减速,减小滑跑所需距离。运用Flash CS3软件对B737飞机液压动力刹车系统工作原理进行模拟仿真,用逐帧动画和补间动画两种方法将液压的流动方向以动画形式直观展现出来。详细分析了在人工刹车的工作方式下正常刹车、备用刹车和蓄压器刹车三种形式的工作过程。将两种仿真方法进行对比,结果表明:逐帧动画制作简单但表现形式欠佳,补间动画虽过程复杂但结果更加直观形象。针对B737飞机起落架刹车系统工作原理的动画模拟仿真,对刹车系统的学习、维修、研究和改进等具有一定的参考价值。     

Optimal sampling for the estimation of dispersion parameters in soil columns using an Iterative Genetic Algorithm

In groundwater modelling, an appropriate soil characterization is strongly recommended to evaluate both the fate and transport of solutes and the performance of groundwater remediation criterion, though parameter estimation techniques are often blocked by several inherent difficulties (i.e. ill-posedness and insufficient quantity and quality of observation data). In this paper, an iterative decision model is built and tested in order to locate the position of a fixed number of sample points in a soil column experiment to obtain optimal parameter estimation (OPE), minimizing the parametric uncertainty and the overall cost of the experimental campaign. Starting from an initial guess of chosen points (given by a fraction of the total disposable ones), an Iterative Genetic Algorithm (IGA) is capable of finding the best points able to minimize a first-order approximation of the parameter covariance matrix. The parameter estimates are updated under a Bayesian scheme, using exclusively the observations collected after the earlier run of minimization, and the iterative process stops when the imposed convergence criterion based on the parameter values is reached. An important contribution of this work is the development of an effective direct search algorithm (IGA) for solving the sampling network optimization problem at a laboratory scale.     

Comparative susceptibility of Corcyra cephalonica (Lepidoptera: Pyralidae) eggs to carbon dioxide and nitrogen at different temperatures

The aim of this study was to evaluate the susceptibility of the egg stage of the rice moth Corcyra cephalonica to modified atmospheres (MAs) enriched with CO₂ or N₂ at 25, 30 and 35 °C combined with various exposure times. The tested modified atmospheres containing CO₂ were 20% CO₂, 16% O₂ and 64% N₂; 40% CO₂, 12% O₂ and 48% N_2; 60% CO₂, 8% O₂ and 32% N₂ and 80% CO₂, 4% O₂ and 16% N₂. The tested modified atmospheres containing N₂ were 97% N₂ and 3% O₂ and 98% N₂ and 2% O₂. The results showed that the hatchability responding to modified atmospheres enriched with either CO₂ or N₂ decreased significantly with an increase in exposure time, gas content (%) and temperature. All tested combinations provided complete (100%) egg control in less than 4 days. Based on 100% mortality, shorter exposures were obtained with 80% CO₂ than with N₂ at most tested temperatures. The modified atmospheres enriched with 98% N₂ were more effective than 97% N₂ against C. cephalonica eggs, especially at 35 °C. It is recommended to use high levels of CO₂ in air (80%) and N₂ (98%) in controlling 0–24-h-eggs of C. cephalonica within 24–36 h for CO₂ and 18–72 h for N₂.     

轮轨材料/硬度匹配研究进展与展望

车轮与钢轨硬度是影响轮轨磨损的主要因素之一,合理的轮轨材料与硬度匹配对于减轻轮轨磨损、延长服役寿命具有十分关键的作用。当前我国铁路运营过程中存在2种硬度钢轨匹配4种硬度车轮的现象,材料匹配行为复杂。针对铁路轮轨材料和硬度的选用与匹配,至今尚无统一合理的规定与标准。从轮轨材料硬度出发,首先分析了国内外轮轨材料发展与硬度匹配的使用现状,发现不同国家和地区轮轨材料硬度的选用存在较大差异。具体表现为:日本新干线使用的车轮硬度远高于钢轨(H_R/H_W<1),欧洲高速铁路上H_R/H_W值接近1,而中国高速铁路系统中,轮轨种类多,硬度区间大。其次,总结了轮轨硬度匹配研究进展,明确材料硬度和轨轮硬度比(H_R/H_W)对磨损与滚动接触疲劳损伤都具有显著影响,但并没有形成统一的结论,且以往的材料选用经验并不完全适用于当前的铁路系统。然后,针对现阶段轮轨材料与硬度匹配研究,探讨了材料加工硬化、合金钢微观组织、表面热处理工艺、复杂服役环境与车轮运行参数等因素的潜在影响。最后,提出...     

石墨烯微片对环氧树脂热性能的影响研究

研究石墨烯微片（GNS）对特种环氧树脂（AG-80/JD-919）的热稳定性和燃烧性能的影响。首先采用溶液共混法将GNS 添加到环氧树脂中,并利用热重分析仪（TGA）和锥形量热仪（CCT）分别对阻燃环氧树脂进行热稳定性和阻燃性能的测试分析。结果表明,GNS 添加量为6%时,环氧树脂的残炭量提高了4.6%,同时峰值热释放速率（pHRR）和总热释放量（THR）分别降低了40.63%和15.43%。因此,GNS 能够改善环氧树脂的热稳定性及其阻燃性能,这主要与GNS 在环氧树脂基体热分解过程能够起到物理阻隔作用有关。     

Polydopamine-Assisted Bi-Functional Modification of NiO Anode for Enhanced Lithium-Ion Storage Performance

The blooming requirement of high-performance energy storage systems has aroused the thirst for advanced energy storage materials. As a high capacity anode, however, the application of NiO nanoparticles (NiO NPs) is hindered by intractable issues of dramatic volume change, intrinsic low electronic conductivity, and severe aggregation tendency during lithiation/delithiation. Herein, a polydopamine (PDA) assisted bi-functionalization strategy for fabricating of PDA@NiO-CNT composites for fast and durable lithium storage is reported. In this composite, CNTs intertwine to form a network to ensure sufficient electrolyte infiltration and act as a highly conductive system to motivate fast charge transmission. The strong binding affinity of PDA facilitates bonding between NiO NPs and CNTs, which not only forms uniform and flexible PDA coating but also ensures homogeneous distribution of NiO NPs on CNTs network. Therefore, the bi-functional modified PDA@NiO-CNT electrode possesses high conductivity, alleviates volume change and aggregation of NiO NPs during cycling, achieves a reversible capacity of 1326 mAh g⁻¹ at 100 mA g⁻¹, a rate capability of 215 mAh g⁻¹ at 2000 mA g⁻¹ and a cycling stability with 78% capacity retention after 250 cycles. This bi-functional modification approach manifests its prospective potential for architecting other electrode materials toward high-performance electrochemical devices.     

Ablation behavior of inorganic particle-filled polybenzoxazine composite coating irradiated by high-intensity continuous laser

Further utilization of aircraft structural materials is threatened by the fact that high-intensity continuous lasers are widely used in the field of military defense. To protect the aircraft structure from laser damage, ammonium polyphosphate filled polybenzoxazine composite coatings were prepared on the substrate. The anti-laser ablation characteristics of the coatings were investigated. Results showed that the addition of the inorganic filler improved the anti-laser ablation performance of polybenzoxazine. The back-surface temperature of substrates covered with the composite coatings was more 50% lower than that in the case of a pure polybenzoxazine coating after laser ablation. Further, the residue of the composite coating could be vertically divided into three distinct regions, with the dense surface char layer and the porous pyrolysis layer acting as shielding layers for the laser beam and preventing any heat-related transformations from occurring. The addition of the inorganic particles improved the surface reflectivity of the coatings resulting in much more laser energy dissipation. The decreased pyrolysis rate ensured that the pneumatic cooling effect of pyrolysis gas was more lasting and stable, owing to which the composite coatings could act as effective thermal protection layer for longer. These results confirmed that the inorganic filler modified polybenzoxazine coating exhibits excellent anti-laser properties and are suitable for protecting structural materials from laser-related damage.     

莫来石纤维增强SiO_(2)气凝胶复合材料压缩回弹性能实验与建模研究EI北大核心CSCD

对莫来石纤维增强SiO_(2)气凝胶复合材料开展面外方向单轴压缩实验,研究不同极限应变、热暴露温度对压缩回弹行为与变形恢复能力的影响,基于微观结构形貌变化阐释内在机制,对加载和卸载阶段的变形行为建立唯像力学模型。结果表明:莫来石纤维增强SiO_(2)气凝胶复合材料的压缩回弹行为呈现非线性特征,极限应变越大,变形恢复能力越差;高温热暴露预处理会对压缩回弹性能产生影响,热暴露温度越高,变形恢复能力越差,基体颗粒-团簇结构的聚集、大尺寸孔洞的形成和塌陷是主要原因;所建立的唯像力学模型可以用来描述材料在压缩加载-卸载时的应力-应变曲线,拟合结果与实验数据吻合较好。     

酚醛树脂/玻璃纤维型飞机货舱衬板复合材料火灾危险性评价

应用锥形量热仪和烟密度箱测试分析飞机货舱衬板在不同火灾环境下的燃烧特性,结合锥形量热仪实验数据对玻璃纤维/酚醛树脂复合材料的火灾危险性进行评价.结果表明:不同热辐射强度对货舱衬板的影响有区别,热辐射强度越大,热分解越快,点燃时间越短,热释放速率峰值越大,最大峰值为98.5 kW/m2,最大总热释放量为7.7 MJ/m2...     

Soot deposition effects and microwave regeneration modelling of diesel particulate filtration system

Regeneration of accumulated soot particles in the substrate walls of the diesel particulate filtration system is one of the major challenges faced by the automotive industry. This study investigated the conversion efficiency and filtration behaviour of the after treatment system comprising of diesel oxidation catalysis (DOC) and diesel particulate filtration (DPF) system. The average conversion efficiency of hydrocarbons was close to 54% and filtration efficiency of the particle number emissions was around 92%. Characterization of the DOC and DPF substrate were conducted using microscopic imaging, Fourier transform infrared spectroscopy (FTIR) and particle size analysis (PSA). The results of FTIR study indicated the presence of carcinogenic agents trapped in the porous walls of the filter substrate. A model for microwave based regeneration system is proposed in this article and CFD analysis were conducted to determine the temperature and electric field distribution in the DPF substrate for a regeneration time of 180 s. Results of simulation showed that the microwave radiations raise the temperature close to soot oxidation temperature (873 K), ensuring effective regeneration.