飞船返回舱座椅缓冲系统的改进与优化设计

为改善返回舱座椅缓冲系统的性能,提出一种新的改进方案,将其脚部由铰接支撑改为斜置弹性支撑。在ADAMS中建立座椅缓冲系统的动力学模型,并采用参数化建模方法对斜置弹性支撑的参数进行优化设计。对优化后的座椅缓冲系统进行动力学仿真的结果表明,与改进前座椅系统的缓冲性能相比,优化后的座椅缓冲系统不仅没有增加胸背向冲击响应,而且显著改善了人体头盆向的冲击响应。     

载人飞船着陆座椅缓冲系统的动力分析与改进

现有载人飞船座椅采用前支座铰接的方式,只能实现单向着陆缓冲。为了减小着陆过程对航天员的多向冲击过载,在此将座椅支座铰链连接改为双向弹性支撑。建立了两种缓冲系统的动力学模型,在同一种着陆工况下,比较了两种缓冲方案的缓冲器行程、工作时间、胸—背向和头—盆向加速度的动态响应。算例表明,改进后的缓冲系统能降低多向冲击加速度峰值。     

一种返回舱座椅水平缓冲杆设计

在对典型"联盟式"返回舱座椅局部改进的基础上,建立了能够吸收水平着陆冲击能量的水平缓冲杆支撑座椅模型。基于胀环式缓冲杆的缓冲原理和工作特性,定义了典型、极限水平着陆工况和水平缓冲杆设计要求;应用三部分设计方案和优化选择程序,分别设计了各段胀环长度相等和不相等的水平缓冲杆。座椅实例设计结果表明,综合了着陆工况、缓冲原理、工作特性和优化效率各个影响因素的设计方法,具有统一、全面和高效的特点;优化的水平缓冲杆支撑座椅,实现了同时缓冲头盆向和胸背向过载、适应更宽着陆工况的目的。     

载人防护缓冲气囊座椅的优化设计

针对设备载人空投过程中乘员防护的问题,设计出一种对乘员人体进行防护的缓冲气囊座椅,并采用MADYMO软件建立了缓冲气囊座椅数值模型,模拟该设备载人空投着陆中缓冲气囊座椅对乘员的缓冲过程。以减少人体的颈部损伤和胸部损伤为优化目标,利用微型多目标遗传算法对缓冲气囊座椅的充气质量、排气孔面积、排气压差以及缓冲气囊护颈的充气质量进行优化。该优化设计不但可以减少气囊座椅设计实验次数从而降低实验的成本,而且在载人空投防护技术领域具有一定的实际工程意义。     

主动磁悬浮轴承支承旋转机械的减振性能研究

针对旋转机械的振动噪声问题,在对轴承工作特性及系统振动传递特性进行理论分析的基础上,提出了采用新型主动磁悬浮轴承取代传统机械轴承以实现整机减振降噪的设想.以某工程试验样机为研究对象,利用有限元软件考察了轴承的刚度变化对该样机轴承座机脚振动不平衡响应的影响,进而开展了专门的振动对比实验来对主动磁悬浮轴承的减振性能进行实际评估.结果表明:减小轴承刚度的思路对于降低旋转机械的机脚振动确实可行;相比于机械轴承,采用主动磁悬浮轴承支承对于减小整机振动水平具有显著实际效果.相关结论可为拓展主动磁悬浮轴承技术的应用领域和场合提供重要思路及数据支持,同时也为其今后的工程化实用奠定研究基础.     

碳纤维复合材料孔隙率超声衰减测试研究

探讨和分析了碳纤维复合材料孔隙率检测的各种方法以及理论方面的研究,指出材料内部孔隙形状与孔隙含量存在着相关性,孔隙含量超声衰减测量应考虑孔隙形貌因素,超声波频率因素对超声衰减孔隙含量测量存在着影响,不同频率超声波影响着超声衰减孔隙含量计算公式的具体形式,复合材料孔隙率检测的难点在于破坏性实验及孔隙特性不能与实测中超声信号充分点点对应,不能有效充分考虑孔隙特性,提出了一种基于孔隙特征的多分段拟合孔隙率超声衰减测试方法,并以一简单例子对多分段拟合结果进行了分析.     

某型飞机双座弹射轨迹仿真分析

以HTY-8座椅为原型,建立了具有轨迹发散作用的仿真模型,通过仿真,比较分析了发散火箭在不同冲量和不同弹射条件下对弹射轨迹的影响。仿真结果表明,在零速度或速度较低的弹射条件下,采用发散火箭是必要的。在中高速弹射条件下,由于前后座椅弹射具有一定的时间差,X方向轨迹离散,前后座椅弹射轨迹发散,发散火箭的作用并不明显,尚需进一步分析人椅分离后先弹射的座椅的运动轨迹。在不利姿态弹射条件下,横滚时发散火箭作用并不明显,俯冲时则能够起到轨迹发散作用。     

穿孔管消声器横截面模态及消声特性的有限元分析

将有限元法应用于计算穿孔管消声器的横截面模态频率,推导了相应的有限元公式并编写了计算程序。对于圆形同轴结构的模态频率,有限元法计算结果与解析法计算结果吻合良好,表明了有限元法预测穿孔管消声器横截面模态的准确性。之后将有限元法应用于计算和分析孔径、穿孔率和穿孔管偏移对直通穿孔管消声器横截面模态和消声特性的影响。结果表明,穿孔率低于40%时,孔径减小或穿孔率增大均能使(0,1)阶模态频率升高,消声器中频消声效果变好;穿孔率高于40%后,孔径和穿孔率对(0,1)阶模态频率影响较小。对于非同轴结构,平面波截止频率为第2阶模态频率,对于给定的孔径和穿孔率,穿孔管偏移对第2阶模态频率影响较小。     

Haze removal method based on a variation function and colour attenuation prior for UAV remote-sensing images

Aiming at the problem of low visibility of images obtained by UAV in hazy weather, this paper proposes an image dehazing algorithm based on variation function and colour attention prior. A large number of experiments have proved that the sky or other bright regions could affect the estimation of atmospheric light and transmittance. In the experiment, our proposed algorithm divides the images into sky and dark regions and uses the pixels of the dark region to solve the atmospheric light value. According to the region where the pixels are located, the transmittances of the pixels in the sky and non-sky regions are separately estimated and adjusted. The experiment’s results show that the restored image visibility, information entropy and colour saturation are significantly improved, and the algorithm’s computational efficiency is high.     

汽车悬架及司机座椅动态参数优化

汽车悬架及司机座椅动态参数对汽车行驶的平顺性有着重要影响。本文以八自由度三维空间质弹系统作为汽车振动系统的力学模型，用前后四轮路面随机激励作为系统输入，对车厢及司机座椅的输入功率谱进行分析，在此基础上对该模型的悬架及司机座椅动态参数进行优化，并给出悬架参数及司机座椅参数的优化结果。     

袖套式挠性接管性能及管路减振效果的试验研究

本文对袖套式挠性接管的平衡性能、静刚度参数及阻抗特性进行了试验研究 ,并在试验室用船用往复式舱底泵对袖套式挠性接管进行了不同压力状态下的管路减振效果的试验 ,试验结果表明袖套式挠性接管具有良好的减振效果和实船运用前景。     

光互联网中新型双向OXC的串扰分析

本文基于光纤布喇格光栅和光环行器提出了2×2双向光交叉连接器光串扰分析模型.分析了基于新型模型的相干串扰与非相干串扰的原理、特性以及它们对系统性能的影响.我们采用蒙特卡洛方法进行仿真实验,仿真结果表明,新型双向光交叉连接器的相干串扰将随着波长数的增加而增加且具有较小的功率代价特性.这种新型的双向光交叉连接器通过级联可扩展到N×N的波长路由.它在未来的全光网络中有较好的应用前景.     

Sustainability of the effects of the demerit points system on seat belt use: a region-wide before-and-after observational study in Italy

To assess the short and long term effects of the demerit points system on seat belt use, we set a region-wide cross-sectional observational study 3 months before, and 3 and 15 months after the introduction of the scheme (July 2003) in the Veneto Region, Italy. We analysed differences in seat belt use by year of observation, gender and position in the vehicle, and obtained adjusted prevalence ratio (APR) through Poisson regression. A total of 29,303 drivers, 28,778 front and 12,186 rear passengers were observed. Prevalence levels of 54% for drivers and 53% for front passengers in 2003 switched to 83 and 76%, respectively, 3 months after the new legislation, with further slight increases 15 months thereafter. Seventy-four percent rear passengers were still not compliant with the legislation in 2005. The probability of being belted was 25% lower in males than females (APR=0.75, 95% CI 0.73-0.77) at the beginning of the study period. However, the effect of the new legislation was 19% greater among males (APR=1.19, 95% CI 1.16-1.23). A substantial increase in seat belt use was reached and sustained with the demerit points system. Specific efforts should target rear passengers whose seat belt use still remains worryingly low.     

Topology optimization of muffler internal partitions for improving acoustical attenuation performance

The internal partition configuration of an expansion chamber muffler affects significantly its acoustical transmission characteristics, but the use of systematic optimization methods to muffler design problems is rare. The main objective of this research is to maximize the transmission loss at target frequencies by optimizing partition layouts inside a muffler chamber by formulating an acoustical topology optimization problem. The selected target frequencies include the deep frequencies of a nominal muffler in order to see the critical effects of partition configurations on the acoustical transmission characteristics. The effects of partition volume constraint ratios are also investigated and physics behind the optimized layouts is investigated. Numerical results show that mufflers with optimized partition layouts outperform nominal mufflers considerably, but the shapes and locations of the optimized partitions should be much different from those of conventional partitions. Copyright © 2009 John Wiley & Sons, Ltd.