云模型改进惯性权重的混沌交替粒子群算法

标准粒子群算法通过线性减小惯性权重系数来调整寻优性能,但缺乏智能化机制易导致算法后期产生早熟或陷入局部最优而产生僵局。针对这一问题,提出一种基于云模型改进惯性权重的混沌交替粒子群优化算法。根据粒子迭代变化关系,采用云模型理论对惯性权重ω进行智能化调整,以平衡其全局和局部搜索能力,防止算法产生局部僵局;另外,判定粒子稳定性,对于可能陷入局部僵局的稳定粒子进行混沌扰动,促使其跳出僵局进而向最优位置更新。实验与分析表明,基于云模型改进惯性权重的混沌交替粒子群优化算法能够跳出局部僵局且具有较高的寻优精度,算法接近完全收敛时的平均迭代次数,较现有相关研究分别降低了13.73%~20.11%。     

Si3 N4基复相陶瓷天线罩材料的制备及性能

基于高马赫数导弹天线罩为应用背景,以Si粉、BN粉、SiO2粉为主要原料,采用反应烧结法制备Si3N4基复相陶瓷材料,探讨了原料组成、成型工艺及坯体密度对材料性能的影响。试验结果表明:当原料中Si、BN和SiO2分别为55%、30%和10%时,材料强度可达96.7MPa,断裂韧性可达1.80MPa.m1/2。同时材料具有良好的介电性能及热物理性能。     

碳化硼涂覆的碳纤维的抗热氧化性研究

用自己合成的裂解能得到碳化硼的聚碳硼烷,对碳纤维进行涂层,并详细测试了涂层碳纤维的抗热氧化性能。     

Bioprotection of facilities

The anthrax attacks of 2001 energized research directed toward reducing health consequences from airborne contaminants by augmenting current heating ventilation and air-conditioning (HVAC) systems. Even during peacetime, interest will continue in improving HVAC components to reduce biocontaminants associated with sick building syndrome. Current HVAC design uses numerical simulation methods of ordinary differential equations to predict approximate performance. The authors show that state-space Laplace Transform calculations actually solve the underlying differential equations and yield algebraic expressions that provide new insight. To sharpen the arguments in favor of this methodology, attention is restricted to improving existing HVAC systems to increase protection from an external release of hazardous particulates. By nearly eliminating the need for dynamical simulation, the resulting methods can be applied to far more complex HVAC designs with little additional computational effort. The new methods reduce the time required for computation by three orders of magnitude. These algebraic methods also can be extended to disparate technical problems including internal particulate release, gas masks, and designing new protective buildings.     

用B4C陶瓷先驱体涂复碳纤维研究

用溴苯和BF3乙醚为起始原料,合成出聚对亚苯基硼(PPB),高温裂解后得到含B4C 54.4%、B2O2 13.6%、自由碳32%的陶瓷.用溶液浸涂碳纤维(CF)并高温裂解后得到B4C涂层CF,与未涂层CF相比,B4C涂层CF抗热氧化性提高200°C.1800°C热压时B4C涂层CF较未涂层CF制得的CF/SiC复合材料的σb值提高10.5% ,KIC值提高19.4%,1850°C热压时相应的σb值提高31.6%,KIC提高5.8%.     

Preparation and characterization of HMX/EVA/hBNNSs micro-composites with improved thermal stability and reduced sensitivity

Hexagonal boron nitride nanosheets(HBNNSs)have huge potential in the field of coating materials owing to their remarkable chemical stability,mechanical strength and thermal conductivity.Thin-layer hBNNSs were obtained by a liquid-phase exfoliation of h-BN powders and incorporated into EVA coatings for improving the safety performance of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane(HMX).HBNNSs and ethylene-vinyl acetate copolymer(EVA)were introduced to HMX by a solvent-slurry process.For com-parison,the HMX/EVA and HMX/EVA/graphene(HMX/EVA/G)composites were also prepared by a similar process.The morphology,crystal form,surface element distribution,thermal decomposition property and impact sensitivity of HMX/EVA/hBNNSs composites were contrastively investigated.Results showed that as prepared HMX/EVA/hBNNSs composites were well coated with hBNNSs and EVA,and exhibited better thermal stability and lower impact sensitivity than that of HMX/EVA and HMX/EVA/G composites,suggesting superior performance of desensitization of hBNNSs in explosives.     

固冲补燃室团聚硼颗粒燃烧试验

研究团聚硼颗粒在补燃室中的点火燃烧对提高固冲发动机性能具有重要意义。通过试验模拟固冲发动机工作过程的方法,开展了补燃室流场条件下的团聚硼颗粒点火燃烧试验。结合高速火焰图像处理技术和流场参数测量结果,对试验中团聚硼颗粒的点火燃烧状态、火焰结构以及颗粒尺寸变化等进行了分析,获得了补燃室燃气温度和氧气含量等因素对团聚硼颗粒点火燃烧过程的影响机制。对燃烧残渣进行了分析,发现燃烧前后颗粒尺寸变化不大,燃烧过程中高温气流可能进入了颗粒内部并与硼颗粒发生反应。     

相对静止气氛下硼颗粒着火过程

针对相对静止气氛下单颗粒硼的着火过程展开了系统研究,考虑硼颗粒周围径向气相流动以及硼颗粒与周围环境间的传热和传质过程,建立了一维硼颗粒着火模型。分析了硼颗粒在实现着火和未能实现着火两种典型情形下的颗粒相、气相组分参数以及颗粒外表面上Stefan流的变化规律,并对其成因展开了分析。研究表明,在实现着火和未能实现着火两种典型情形下,硼颗粒外表面的Stefan流都会经历先由周围空间流向颗粒表面,而后变为由颗粒表面流向周围空间的过程;考虑颗粒外表面处气相Stefan流作用后,硼颗粒的着火延迟时间减少,且压力越大,影响越大。     

碳化硼表面金属化初步研究

为了降低碳化硼(B,C)与金属钎焊连接的温度,采用真空熔结Al基钎料的方法,在1000℃时对其进行了表面金属化处理,SEM和EDAX观察分析B4C与钎料结合断面的形貌和元素面分布,发现B4C与钎料界面发生了互扩散,界面结合致密,形成冶金结合.     

非均匀形核法制备Cu包覆纳米SiO2复合粉体

采用非均匀形核法制备了Cu包覆纳米SiO2复合颗粒,利用X射线衍射仪、扫描电镜、能谱仪及透射电镜等分析手段对复合颗粒进行了表征,并探讨了包覆结构的形成机制。结果表明:复合颗粒分散均匀,无团聚,单颗粒内包含多个分布均匀的纳米SiO2颗粒,且均被Cu包覆层隔离,纳米SiO2颗粒的分散性得到了显著改善;新制备的复合颗粒不存在氧化,在存放或者制样过程中会部分氧化为Cu2O;纳米SiO2颗粒表面Cu包覆层的形成机制主要是非均匀形核作用,包覆的结构取决于 Cu晶粒在纳米SiO2颗粒表面的沉积以及对复合颗粒的团聚控制。