基于人工神经网络的驾驶员操纵行为模型

驾驶员操纵行为受到自身、外界环境和被控对象等多方面的影响,因此驾驶员模型具有非线性的特征。神经网络模型克服了拟线性模型不能反映驾驶员非线性操纵的问题。为了获得建立模型的数据,利用地面模拟器使飞行员对一系列指令进行精确跟踪。获得的指令、飞机状态和驾驶员输入信息等参数即可作为神经网络模型的训练样本。神经网络驾驶员模型的训练和测试结果表明,该建模方法是合理、准确的,可以应用于人机闭环系统中驾驶员操纵的研究。     

B93铝合金热加工特性模拟研究

在Gleeble1500热模拟机上采用轴对称等温压缩实验,研究了B93铝合金在热加工中变形温度和应变速率对合金组织的影响,基于动态模型计算出B93铝合金加工图,分析合金热加工的流变失稳区并确定了合金热加工的最佳工艺参数。结果表明:变形速率和变形温度对B93铝合金的微观组织有影响;合金的峰值应力随变形温度的升高而降低,随变形速率的提高而增大;B93铝合金最佳的热加工制度为:变形温度420℃左右,应变速率0.001 s-1。     

考虑组织因素的航空维修差错产生机理分析

为有效防范航空维修差错的发生,从组织因素角度对航空维修差错产生机理进行分析,在对组织因素影响维修差错作用关系分析的基础上,建立了组织因素导致维修差错的成因机理分析模型,从差错产生的潜伏阶段、发生阶段、纠正或扩展阶段和致灾阶段4个阶段对差错产生的演化过程进行了分析,进一步构建了组织层面的维修差错防控体系,为维修差错的系统...     

7B04铝合金蠕变过程中析出相的影响因素

进行了7B04-T7451铝合金在不同蠕变温度、不同应力水平下的多组蠕变实验,根据蠕变率的变化,得到了合理的蠕变温度为150℃;在此温度下进行了不同应力水平和时效时间下的多组蠕变实验,分析了加工条件对微观组织和力学性能的影响.结果表明,高的应力水平能加速合金强化相的析出和转变,同时增大位错的流动能力,因此,随着蠕变时间的增加,材料的屈服强度呈先上升后加速下降的趋势.     

Comparison of Diurnal,Seasonal and Solar Cycle Variations of High-latitude,Mid-latitude and Low-latitude Ionosphere

Comparison of regular (diurnal, seasonal and solar cycle) variations of high-latitude,mid-latitude and low-latitude ionospheric characteristics has been provided on basis of local empirical models of the peak electron density and the peak height. The local empirical models were derived from the hand-scaled ionogram data recorded by DPS-4 digisondes located at Norilsk (69°N, 88°E), Irkutsk (52°N, 104°E) and Hainan (19°N, 109°E) for a 6-year period from December, 2002 to December, 2008. The technique used to build the local empirical model is described. The primary focus is diurnal-seasonal behavior under low solar activity and its change with increasing solar activity. Both common and specific features of the high-latitude (Norilsk), mid-latitude (Irkutsk) and low-latitude (Hainan) regular variations were revealed using their local empirical models.      

SiO2-水纳米流体在波壁管内流动特性的实验研究

实验研究了不同质量分数的SiO2-水纳米流体在波壁管内的流动特性,由于波壁管自身的结构特点,使流体在较小雷诺数下达到湍流状态,可以方便测出流体在层流、过渡流、湍流区的流动特性.研究发现:相同温度条件下,纳米流体的粘度随着质量分数的提高而增大;流动可视化照片显示纳米流体中由于内部纳米粒子的微运动促使流体均匀性更好;沿程阻力测试表明在层流区内摩擦系数随纳米流体质量分数的增加而增大,在过渡流和湍流区内摩擦系数随质量分数增加变化不大.     

硅化物涂层对铌钨合金的热防护行为研究

钨合金作为轨姿控液体火箭发动机推力室身部的主要结构材料,在工作环境中易发生氧化粉化,必须在合金表面涂覆高温抗氧化涂层。利用涂覆及真空烧结复合工艺在铌钨合金表面制备高温抗氧化涂层,研究硅化物涂层对铌钨合金的热防护行为,包括涂层成型过程、高温抗氧化行为、高温抗热震行为及试车热冲刷行为等,试验结果为:涂层在1700℃下的氧化寿命为11±0.78 h,1800℃下的氧化寿命为5±0.46 h,1650℃~室温的水冷热震循环次数为124±9次,1600~800℃下的空冷热震循环次数为3410±124次,并且在热试车考核中涂层通过了长程10000 s的考核,分析硅化物涂层的性能和失效机制,总结了硅化物涂层的热防护机理,研究的新型硅化物涂层在高温条件下具有较好的性能。     

Experimental,analytical and numerical investigation on tensile behavior of twisted fiber yarns

Stitched composite materials are emerging as a promising material due to their high interlaminar strength, combined performance and light weight. The mechanical properties of stitch yarns are very essential for stitched composite structures. In this study, the tensile behaviors of the twisted fiber yarn in stitched composites were investigated experimentally, analytically and numerically. Two kinds of cross-sectional area of twisted yarn are proposed and discussed. The paper presents an intersecting circle model to describe the cross-section of twisted fiber yarns, and a physics-based theoretical model to predict the effective tensile moduli. The numerical models take into account the cross-sectional characteristic and the twist architecture. The investigation shows that: the sum of each fiber area should be used for experimental analysis; and the cross-sectional area surrounded by the yarn profile should be used for theoretical predictions and finite element (FE) simulations. The relative errors of the prediction method and the FE simulation are less than 2% and 1%, respectively. The friction between the fibers is derived, and the effect of friction on mechanical properties is discussed. The investigation method will serve as a fundamental component of twisted fiber bundle/yarn analysis.     

Transient thermal behavior of stratospheric balloons at float conditions

The prediction of the thermal behavior of stratospheric balloons under varying environmental conditions is one of the key issues in the design and flight test of balloons. In this paper, a three-dimensional transient thermal model is developed to predict the thermal behavior of spherical stratospheric balloons. The diurnal variations of the skin and lifting gas temperatures at float conditions are discussed in detail. The further studies on the thermal behavior of stratospheric balloons are presented also.     

平纹编织C/SiC复合材料在室温和高温环境下的拉伸行为

通过单向拉伸试验,对比研究平纹编织C/SiC陶瓷基复合材料在室温和高温(1300℃,包括惰性气氛和湿氧气氛)环境下的宏观力学特性,并采用光学显微镜和扫描电镜对试件断口进行显微观察,分析其损伤模式和破坏机理。结果表明:C/SiC复合材料的室温和高温拉伸行为通常表现为非线性特征,在低应力时就开始出现损伤;纤维与基体之间界面滑行阻力的降低使C/SiC复合材料在高温惰性气氛环境下的拉伸强度和破坏应变均比室温下的高;碳纤维的氧化严重影响材料的承载能力导致高温湿氧环境下的拉伸强度和破坏应变均比室温下的低;C/SiC复合材料室温和高温下的拉伸均呈现韧性断裂,断口较为相似,只是纤维拔出长度和断口的平齐程度有所不同,其中高温惰性气氛环境下纤维拔出最长,高温湿氧环境下试件断口有明显的被氧化痕迹;0°纤维束表面基体开裂、明显的层间分层以及0°纤维和纤维束的拔出和断裂同时携带90°纤维束拔出是C/SiC复合材料在室温和高温下的拉伸破坏机理。