An integrated graphic–taxonomic–associative approach to analyze human factors in aviation accidents

Human factors are critical causes of modern aviation accidents. However, existing accident analysis methods encounter limitations in addressing aviation human factors, especially in complex accident scenarios. The existing graphic approaches are effective for describing accident mechanisms within various categories of human factors, but cannot simultaneously describe inadequate human–aircraft–environment interactions and organizational deficiencies effectively, and highly depend on analysts' skills and experiences. Moreover, the existing methods do not emphasize latent unsafe factors outside accidents. This paper focuses on the above three limitations and proposes an integrated graphic–taxonomic–associative approach. A new graphic model named accident tree(AcciTree), with a two-mode structure and a reaction-based concept, is developed for accident modeling and safety defense identification. The AcciTree model is then integrated with the well-established human factors analysis and classification system(HFACS) to enhance both reliability of the graphic part and logicality of the taxonomic part for improving completeness of analysis. An associative hazard analysis technique is further put forward to extend analysis to factors outside accidents, to form extended safety requirements for proactive accident prevention. Two crash examples, a research flight demonstrator by our team and an industrial unmanned aircraft, illustrate that the integrated approach is effective for identifying more unsafe factors and safety requirements.     

环境压力对双组分运动液滴蒸发特征影响的理论研究

为获得亚临界条件下,环境压力对双组分运动液滴蒸发特性的影响规律,基于多组分液滴蒸发模型,对癸烷—乙醇二元混合液滴在高温氮气环境下的运动蒸发过程开展模型研究。通过模型计算,获得了液滴内部浓度分布、温度分布和液滴速度随时间的变化;分析了在环境压力0.1MPa和2MPa下,不同浓度液滴温度、尺寸及表面乙醇浓度的变化特征。结果表明:双组分液滴运动蒸发过程中,内部存在显著浓度和温度梯度,传热扩散快于传质扩散。常压环境下,液滴温度经历瞬态加热和平衡蒸发两个阶段,而高压环境下,液滴温度逐渐升高至接近环境温度。双组分液滴蒸发过程中由于组分浓度随时间变化,其无量纲尺寸随时间变化明显偏离"d 2理论";环境压力越高,液滴运动的贯穿距离越短,蒸发速率越慢。乙醇浓度对液滴蒸发速率的影响有两方面:蒸发前期,乙醇浓度越高,液滴蒸发速率越快;而蒸发后期,乙醇浓度越高,液滴蒸发速率反而越慢。     

基于FFT的抑制载波捕获技术

介绍三种基于快速傅里叶变换(FFT)的开环抑制载波捕获技术,并对这些算法进行性能分析及仿真.结果表明,基于FFT的交错符号积分技术,在低符号信噪比时引入的信噪比损失最小,适用于深空接收机中抑制载波捕获.     

基于神经网络的超精密车床圆柱度误差补偿技术研究

根据所研制的超精密亚微米车床的具体特点，提出了一种基于神经网络的工件圆柱度误差补偿方法，并据此建立了误差补偿控制系统，实验结果证明所提方法简单易行，在超精密车削中应用前景广阔。     

Dimension reduction for array processing with robust interference cancellation

We present a robust solution for data reduction in array processing. The purpose is to reduce the computation and improve the performance of applied signal processing algorithms by mapping the data into a lower dimension beamspace (BS) through a transformation. Nulls steering to interference are incorporated into a transformation using the subspace projection technique, and the BS spatial spectrum estimation accuracy is evaluated and maximized with a measure. The derived transformation tries to preserve the full-dimension Cramer-Rao bounds (CRBs) for the parameters of interest while rejecting undesired signals effectively. When compared with an optimal method and an adaptive approach, simulation results show that significant improvements are obtained in terms of BS direction-of-arrival (DOA) estimation root-mean-squared error (RMSE), bias, and resolution probability.     

Ultra-wideband technology and random signal radar: an ideal combination

Ultra-wideband radar and random signal radar are two types of newly-developed radar systems. This paper introduces the special advantages of the combination of ultra-wideband technology and random signal radar to the international radar community. It shows that these two radar systems have a very close relationship in nature and can gain significant benefits from each other. It can be anticipated that the random signal modulated waveform will open many potential possibilities for the applications of ultra-wideband radar systems to civilian operating environments.     

Eclipse插件开发技术浅探

Eclipse平台是一个开放源码的、可扩展的、基于Java的集成开发环境(IDE).Eclipse本身不提供强大的用户功能,其全部功能都是利用其插件(Plug-in)机制来实现的.本文基于Eclipse平台的体系结构,重点分析了在Eclipse平台下进行插件开发的原理,并实现一个简单插件来展示eclipse插件开发的全过程.     

测液体粘滞系数的一种方法

本文介绍了一种测液体粘滞系数的方法－“落球法”，该方法装置简单，原理清楚，有利于拓宽学生的视野，培养和提高学生的实际技能和处理数据的能力。     

Data fusion of multiradar system by using genetic algorithm

Detection system with distributed sensors and data fusion. are increasingly being used by surveillance systems. There has been a great deal of theoretical study on decentralized detection networks composed of identical or non-identical sensors. To solve the resulting nonlinear system, exhaustive search and some crude approximations are adopted. However, those methods often cause either the system to be insensitive to some parameters or the suboptimal results. In this paper, a novel flexible genetic algorithm is investigated to obtain the optimal results on constant false alarm rate data fusion. Using this approach, all system parameters are directly coded in decimal chromosomes and they can be optimized simultaneously. The simulation results show that adopting the proposed approach, one can achieve better performances than the reported methods and results     

Detonation waves induced by a confined wedge

An auto-ignition detonation phenomenon can be initiated by a wedge confined in a channel. A new, self-sustaining, normal detonation wave engine concept is proposed. The detonation processes were numerically modeled with a simplified two-dimensional wedged channel flow that was deemed to emulate a real three-dimensional configuration. The results showed that within certain ranges of incoming flow Mach number or wedge angle, detonation could be self ignited in the channel. The study furthermore investigated the detonation waves based on three different detonation initiation positions. Different configurations of the detonation waves were observed and analyzed. The performance of the different detonation wave configurations was estimated and compared.