The use of ballistic movement as an additional method to assess performance of computer mice

This study investigates an additional method for independently evaluating performance of speed and accuracy of computer mice, based on five parameters of the initial submovement when aiming at a target. This first submovement is known to be carried out in a ballistic manner and hence the Fitts-type aiming movement may be studied by means of the established relationships for ballistic movement. To test the ballistic movement method, eight participants used four different computer mice to execute ballistic movements and Fitts-type aiming movements. Regression tests showed that the Fitts movement time was well correlated with the time and stopping-variable error of ballistic movement, implying that measuring ballistic movement parameters can predict the performance of Fitts-type aiming movements. More importantly, the use of ballistic movement method allows independent assessments of the speed and accuracy, providing additional information for input devices assessment and designs.Relevance to industryThe study illustrates the close correspondence between input device evaluation using the proposed ballistic movement method and Fitts' law. The ballistic movement method allows independent measures of speed and four types of accuracy, which should benefit input devices assessment and designs.     

Computational Investigation of Effects of Grain Size on Ballistic Performance of Copper

Numerical simulations were conducted to compare ballistic performance and penetration mechanism of copper (Cu) with four representative grain sizes. Ballistic limit velocities for coarse-grained (CG) copper (grain size ≈ 90 µm), regular copper (grain size ≈ 30 µm), fine-grained (FG) copper (grain size ≈ 890 nm), and ultrafine-grained (UG) copper (grain size ≈ 200 nm) were determined for the first time through the simulations. It was found that the copper with reduced grain size would offer higher strength and better ductility, and therefore renders improved ballistic performance than the CG and regular copper. High speed impact and penetration behavior of the FG and UG copper was also compared with the CG coppers strengthened by nanotwinned (NT) regions. The comparison results showed the impact and penetration resistance of UG copper is comparable to the CG copper strengthened by NT regions with the minimum twin spacing. Therefore, besides the NT-strengthened copper, the single phase copper with nanoscale grain size could also be a strong candidate material for better ballistic protection. A computational modeling and simulation framework was proposed for this study, in which Johnson–Cook (JC) constitutive model is used to predict the plastic deformation of Cu; the JC damage model is to capture the penetration and fragmentation behavior of Cu; Bao–Wierzbicki (B-W) failure criterion defines the material's failure mechanisms; and temperature increase during this adiabatic penetration process is given by the Taylor–Quinney method.     

Failure and fragmentation of ceramic target with varying geometric configuration under ballistic impact

The failure and fragmentation of monolithic bare alumina 99.5% ceramic target and energy dissipation of steel 4340 projectile have been studied in a series of ballistic experiments carried out, with the incidence velocities in a range, 122–290 m/s. The velocity drop and energy dissipation increased with incidence velocity for 10 mm thick target with damage zone extended upon the whole area of rear face at higher velocities. The ballistic results obtained with the 10 mm thick target have been compared with the ballistic performance of the 5 mm thick target used in a previous study to explore the effects of target thickness on the failure mechanism. A model for the residual velocity of projectile after perforation of the single layered ceramic target has been developed based on the Lambert Jonas model by using the experimental data available for 5 mm and 10 mm thick alumina 99.5% target against 10.9 mm projectile. The residual velocities and damage patterns were reproduced with a reasonable amount of accuracy by a three-dimensional finite element model developed on commercial ABAQUS/CAE. The effect of obliquity and projectile diameter to target thickness ratio (D/T) on ballistic performance has been determined by the numerical simulation model with impact velocity in a range of 300–500 m/s. A spatial variation of ejected fragments velocity at different time steps was plotted to develop a velocity profile for the ceramic fragments coming out of the target. A semi-empirical model has been proposed for residual velocity after perforation of a monolithic ceramic target, relating to the incidence velocity and projectile diameter to target thickness ratio. The monolithic ceramic targets have been investigated for a comparative assessment of energy dissipation by the ceramic layer to eventually design an efficient front layer of a ceramic based composite armour in future studies.     

Electron injection barrier and energy-level alignment at the Au/PDI8-CN2 interface via current–voltage measurements and ballistic emission microscopy

We probe electron transport across the Au/organic interface based on oriented thin films of the high-performance n-type perylene diimide semiconductor PDI8-CN₂. To this purpose, we prepared organic-on-inorganic Schottky diodes, with Au directly evaporated onto PDI8-CN₂ grown on n-Si. Temperature-dependent current–voltage characteristics and complementary ballistic electron emission microscopy studies reveal that rectification at the Au/PDI8-CN₂ interface is controlled by a spatially inhomogeneous injection barrier, that varies on a length scale of tens of nanometers according to a Gaussian distribution with mean value ∼0.94 eV and standard deviation ∼100 meV. The former gradually shifts to ∼1.04 eV on increasing PDI8-CN₂ thickness from 5 nm to 50 nm. Experimental evidences and general arguments further allow to establish the energetics at the Au/PDI8-CN₂ interface. Our work indicates injection-limited current flow in PDI8-CN₂-based devices with evaporated Au electrodes. Furthermore, it suggests chemical reactivity of PDI8-CN₂ with both Au and Si, driven by the lateral isocyano groups.     

基于模糊层次分析法的导弹阵地防护效能评估

运用层次分析（AHP）与模糊数学相结合的方法进行效能评估，建立了导弹阵地的评价指标体系以及三级模糊评判模型，确定了各评价指标的权重，提出了导弹阵地防护效能的量化评判方法。     

Rolling Control Characteristic Experimental Investigation of a Canard Missile with Free-Spinning Tail

A canard configuration is one of basic aerody-namic configurations for guided missile.From anaerodynamic viewpoint,canard effectivenessincreas-es with increasing angle-of-attack(AoA);canardhinge moment is typically smaller thanthe hinge mo-ment for anequivalent tail fin;andcanards reducethetransonic stability rise.From a system design viewpoint,canards can be located near the inertial mea-surement unit(I MU)and flight computer;therebyeli minating the need to route cables to the rear of theai…     

虚拟战场环境的导弹可视化仿真设计

主要对多模复合制导仿真平台中的导弹视景仿真模块的实现方法进行了研究,介绍了仿真模块的组成,研究了三维物体建模的方法并讨论如何实现动态演示。对基于VC＋＋以OpenGL编程建模仿真和采用Creator、Vega实现作战导弹飞行可视化这样两种方法,概括阐述了其实现过程,并进行了分析比较,得到了适用于导弹飞行仿真控制的设计方法,对于其它场景下三维物体仿真具有一定的借鉴作用。     

Recent Developments for Prediction of Power of Aromatic and Non‐Aromatic Energetic Materials along with a Novel Computer Code for Prediction of Their Power

The explosive power or strength of an energetic material shows its capacity for doing useful work. This work reviews recent developments for prediction of power of energetic compounds. A new user‐friendly computer code is also introduced to predict the relative power of a desired energetic compound as compared to 2,4,6‐trinitrotoluene (TNT). It is based on the best available methods, which can be used for different types of energetic compounds including nitroaromatics, nitroaliphatics, nitramines, and nitrate esters. The computed relative powers are consistent with the measured data for some new materials containing complex molecular structures.     

某型导弹自驾仪的故障诊断研究

模拟电路的故障诊断存在着信号非线性、样本初期获取困难等问题,支持向量机技术具有小样本、非线性、全局最优和建立的模型能更好泛化等诸多优点,为解决这些问题提供了一条有效途径。以某型导弹自驾仪中电路为典型例子,在C-SVM基础上构建模糊支持向量机,并采用粒子群算法与遗传算法进行向量机的参数优化。首先采用小波包分解提取故障信息的特征向量并归一化,然后将训练集送入改进后的向量机中完成训练,最后将测试集送入训练好的向量机中完成不同故障模式的识别,故障检测率达到93.3333%。结果表明在样本量较少的情况下,改进后的支持向量机可以很好地完成故障诊断任务。     

亚音速飞行器往复式滑翔增程弹道设计

为增加亚音速巡航导弹的有效航程,提出一种往复式滑翔增程弹道方案。基于已有的气动参数建立水平直飞巡航弹道与往复式滑翔巡航弹道模型,对比分析2种弹道方案的有效航程及其特性,从能量守恒角度出发研究往复式滑翔的增程原理。进一步研究初始飞行马赫数、初始弹道倾角以及初始飞行高度对往复式滑翔弹道增程特性的影响。研究结果表明:往复式滑翔弹道能够有效增加导弹航程,相比于常规水平直飞弹道的最大飞行距离,往复式滑翔弹道的增程效率达到100.42%; 在往复式滑翔弹道能够成功的前提下,初始飞行马赫数越大,初始弹道倾角越小,初始飞行高度越低,往复式滑翔弹道的增程效率越明显。