应用声信号特征识别车辆车型及车速范围*

国内外现有研究工作主要针对车型进行识别,该文在此基础上对车速范围的分类识别进行了研究。文中将主成分分析方法和BP神经网络算法结合(PCA-BP)对车型与车速进行识别分析,对比了与BP神经网络算法识别速度的差异。结果表明应用PCA-BP方法的识别效果整体较好,且在识别过程中可以节省计算时长的50%～70%左右,大大提高了识别速度。在未来的车辆识别系统实现中,可以在保证良好识别效果的前提下,提高软硬件平台的传输效率,节省识别计算时间。     

Ultrafine grain formation and coating mechanism arising from a blast coating process: A transmission electron microscopy analysis

This article examines the substrate/coating interface of a coating deposited onto mild steel and stainless steel substrates using an ambient temperature blast coating technique known as CoBlast. The process uses a coincident stream of an abrasive blast medium and coating medium particles to modify the substrate surface. The hypothesis for the high bond strength is that the abrasive medium roughens the surface while simultaneously disrupting the passivating oxide layer of the substrate, thereby exposing the reactive metal that then reacts with the coating medium. The aim of this study is to provide greater insight into the coating/substrate bonding mechanism by analysing the interface between a hydroxyapatite coating on both mild and stainless steel substrates. The coating adhesion was measured via a tensile test, and bond strengths of approximately 45 MPa were measured. The substrate/coating interface was examined using transmission electron microscopy and selected area diffraction. The analysis of the substrate/coating interface revealed the presence of ultrafine grains in both the coating and substrate at interface associated with deformation at the interface caused by particle impaction during deposition. The chemical reactivity resulting from the creation of these ultrafine grains is proposed to explain the high adhesive strength of CoBlast coatings.     

钢框架中组合楼盖的面内变形

为了研究影响钢-混凝土组合框架中组合楼盖隔板性能的因素,以楼板厚度、框架侧移刚度以及结构平面刚度布置为参数对钢框架中的组合楼盖进行了弹性有限元分析．分析结果表明,除长宽比外,组合楼盖的隔板性能还与其面内刚度以及支撑体系的特性有关．根据分析结果提出了组合楼盖隔板性能的评价方法, 并与试验结果进行了验证．该方法可以为工程实践中评价组合楼盖的隔板性能作参考．     

羟基硅酸盐润滑油添加剂对45#钢/球墨铸铁摩擦副摩擦磨损性能的影响

采用MM-200型摩塔磨损试验机考察了45^#钢／球墨铸铁摩擦副在650SN基础油和含羟基硅酸盐矿物复合微粉的650SN基础油(KF-1)润滑下的摩擦磨损性能，结果表明：在650SN基础油润滑下的摩擦系数和磨损率随试验时间增加变化较小；而在KF-1润滑下，试验初期的摩擦系数和磨损率比基础油润滑下的稍大，随着试验时间的延长，相应的摩擦系数和磨损率同基础油润滑下的相比明显降低．磨损表面显微硬度测试结果表明，在KF-1润滑下45^#钢磨损表面形成了多孔摩擦改性层，硬度明显提高，因而摩擦磨损性能显著改善．     

Stability and Oscillations in a Time-Delayed Vehicle System with Driver Control

In this paper, linear stability and chaotic motion of a time-delayednonlinear vehicle system are studied. The stability is determined bycomputing the spectrum associated with a system of linear retardedfunctional differential equations, which reveals that a loss ofstability occurs following a Hopf bifurcation. Beyond the critical valuefor linear stability, the system exhibits limit cycle motions.Subharmonic, quasi-periodic and chaotic motions are observed for asystem excited by a periodic disturbance.     

汽车碰撞砼护拦过程的数值模拟

将汽车与砼护拦简化为刚体，给出了描述碰撞过程中车辆三维空间运动的Ｅｕｌｅｒ－Ｌａｇｒａｎｇｅ方程－微分代数方程组，采用半显式外插方法求解上述方程组。数值计算得出的车辆各方向上的最大平均加速度、最大侧倾角、最大俯仰角、车轮沿护拦面的最大爬升值及车辆脱离护拦时的弹出角等结果是从乘员风险和车辆轨迹等多角全面评估砼护拦的安全性能的重要依据。针对美国ＮｅｗＪｅｒｃｙ型砼护拦的实际算例与文献结果吻合较好。     

腐蚀磨损协同作用率的研究

提出了腐蚀与磨损“协同作用”的概念，并用于判断腐蚀与磨损协同作用的性质及大小和确定腐蚀磨损过程中材料损失的主要形式。介绍了协同作用率的测定方法，并以Ｇ１０５钢及化学镀Ｎｉ－Ｐ合金在５．０％ＮａＣｌ溶液中的腐蚀腐损作为研究对象，研究了载荷、滑动速度对腐蚀磨损协同作用的影响。结果表明：协同作用率随载荷增大而增大，随滑动速度增大而减小。     

飞机起落架活塞杆断裂原因分析

针对飞机起落架活塞杆在外场使用过程中裂纹失效问题,利用扫描电子显微镜对其断裂面微观形貌进行观察,研究其断裂机理.结果表明:该活塞杆断裂性质为服役过程中循环应力作用下的疲劳断裂.应力使活塞杆件表面出现微裂纹,在其内部形成微孔.随着应力循环次数增加,微孔的数量和大小都不断增加,最终导致了钢的疲劳断裂.通过优化其热处理工艺,使活塞杆获得良好的强韧配比,提高了抗疲劳性能.     

Effect of acetic acid on CO2 corrosion of carbon steel in NaCl solution

Potentiodynamic sweep and electrochemical impedance spectroscopy measurements were applied to investigate the effects of both temperature and acetic acid (HAc) on the anodic and cathodic reactions in CO₂ corrosion of P110 steel in 3.5% NaCl solution. The temperatures were controlled at 30 and 60 °C. The concentrations of HAc were controlled at 0, 1000, 3000 and 5000 ppm. In this work, the corrosion parameters of polarization curves, such as corrosion potential (E_corr), corrosion current density (i_corr), and anodic and cathodic branch slopes (b_a and b_c), are presented and discussed in detail. In addition, the equivalent circuit models and ZsimpWin software were utilized to discuss the Nyquist plots. The plots showed that the E_corr values shifted in the positive direction as the HAc concentration increased. The i_corr values increased with the increase in HAc concentration, indicating that HAc could accelerate the corrosion. The impedance spectra measured at 30 and 60 °C have different time constants and characterization. The coverage fraction θ and the thickness L of corrosion film are two most important controlled variables that influence and control the CO₂ corrosion mechanisms. Copyright © 2010 John Wiley & Sons, Ltd.     

Molecularly imprinted polymer coated on stainless steel fiber for solid-phase microextraction of chloroacetanilide herbicides in soybean and corn

A molecularly imprinted polymer (MIP) with metolachlor as template was firstly coated on stainless steel fiber through chemical bonding strategy to solve the fragility problem of silica fiber substrate for solid-phase microextraction. The surface pretreatment of stainless steel fiber and the polymerization conditions were investigated systematically to enhance the preparation feasibility and MIP coating performance, and then a porous and highly cross-linked MIP coating with 14.8-μm thickness was obtained with over 200 times re-usability which was supported by non-fragile stainless steel fiber adoption. The MIP coating possessed specific selectivities to metolachlor, its metabolites and other chloroacetanilide herbicides with the factors of 1.1–4.6. Good extraction capacities of metolachlor, propisochlor and butachlor were found with MIP coating under quick adsorption and desorption kinetics, and the detection limits of 3.0, 9.6 and 38 μg L⁻¹ were achieved, respectively. Moreover, the MIP-coated stainless steel fiber was evaluated for trace metolachlor, propisochlor and butachlor extraction in the spiked soybean and corn samples, and the enrichment factors of 54–60, 27–31 and 15–20 were obtained, respectively.