可控震源重锤-活塞杆动态行为规律与扰动控制研究

针对工程应用中可控震源振动器扰动量大、信噪比低等问题,结合重锤运动轨迹检测试验,通过理论计算与数值模拟,开展了重锤-活塞杆动态行为规律研究;在此基础上,开展振动器扰动控制研究,提出竖直进油方式振动器,与横向进油时的结果开展对比仿真分析,并进行竖直进油振动器扰动试验验证。结果表明:横向进油方式下,重锤受绕z轴的转动力矩作用且活塞杆存在变形,导致重锤上某点的运动轨迹为空间曲线,增大了振动器的扰动量,因此,横向进油方式是导致振动器扰动大的直接原因;竖直进油方式下,重锤不再受转动力矩影响且活塞杆变形得到极大改善,有效降低了振动器扰动量。研究结果对改善输出信号品质、提高输出信号分辨率具有重要的工程意义,建议在振动器的设计中采用竖直进油方式。     

Displacement field denoising for high-temperature digital image correlation using principal component analysis

Principal component analysis (PCA) was extended to minimize the noise effect in digital image correlation (DIC) measurement under a high-temperature atmosphere environment. First, the principle of PCA was introduced, and the singular vectors and singular values for each component of the displacement fields from DIC were obtained. Then, the simulated high-temperature speckle images were developed to investigate the influences of noise on the DIC method under a high-temperature environment. Finally, the displacement fields of several special conditions were extracted from the simulated speckle images and experimental images; the effects of noise on the PCA were also analyzed.     

Targeting orthotopic gliomas with renal-clearable luminescent gold nanoparticles

A major clinical translational challenge in nanomedicine is the potential of toxicity associated with the uptake and long-term retention of non-degradable nanoparticles (NPs) in major organs.The development of inorganic NPs that undergo renal clearance could potentially resolve this significant biosafety concern.However,it remains unclear whether inorganic NPs that can be excreted by the kidneys remain capable of targeting tumors with poor permeability.Glioblastoma multiforme,the most malignant orthotopic brain tumor,presents a unique challenge for NP delivery because of the blood-brain barrier and robust blood-tumor barrier of reactive microglia and macroglia in the tumor microenvironment.Herein,we used an orthotopic murine glioma model to investigate the passive targeting of glutathione-coated gold nanoparticles (AuNPs) of 3 nm in diameter that undergo renal clearance and 18-nm AuNPs that fail to undergo renal clearance.Remarkably, we report that 3-nm AuNPs were able to target intracranial tumor tissues with higher efficiency (2.3x relative to surrounding non-tumor normal brain tissues) and greater specificity (3.0x)than did the larger AuNPs.Pharmacokinetics studies suggested that the higher glioma targeting ability of the 3-nm AuNPs may be attributed to the longer retention time in circulation.The total accumulation of the 3-nm AuNPs in major organs was significantly less (8.4x) than that of the 18-nm AuNPs.Microscopic imaging of blood vessels and renal-clearable AuNPs showed extravasation of NPs from the leaky blood-tumor barrier into the tumor interstitium.Taken together,our results suggest that the 3-nm AuNPs,characterized by enhanced permeability and retention,are able to target brain tumors and undergo renal clearance.     

Modelling and joint monitoring of input and output of systems with arbitrary order autoregressive disturbance

Considerable studies have been done on modelling and joint monitoring of input and output of systems with autoregressive moving average (ARMA) disturbance. Most of these studies focus on systems with ARMA (1, 1) disturbance. However, many kinds of systems are not conform to ARMA(1, 1) disturbance. Motivated by the fact that an autoregressive (AR) model with high order can be implemented to approximate the stationary ARMA model at any precision, a new generic model and a joint monitoring scheme of systems with arbitrary order AR(p) disturbance are developed. A minimum mean squared error (MMSE) controller with arbitrary order AR disturbance is designed to reduce the system variability. The mathematical expectation and average run length of MMSE-controlled outputs are derived. A new joint chart for monitoring the input and output simultaneously is explored. Two out-of-control rules for the joint monitoring chart are developed. The monitoring performances of the input chart, the output chart and the joint monitoring chart are also discussed. The results of simulation experiments and case studies validate the effectiveness of the developed model and joint monitoring chart.     

被动定向浮标阵定位误差仿真分析

仿真分析了被动定向浮标阵为正三角形阵时,阵元间距等几种因素对利用最小二乘法解算目标位置精度的影响。仿真结果表明,在相同的位置误差和测向误差下,当目标在一定范围内时,阵元间距增大,定位误差增大,当目标位置超出该范围后,浮标阵定位误差急剧增大,阵元间距大的浮标阵定位误差反而小;在其它条件相同时,位置误差(测向误差)增大,定位误差增大。因此,为提高三角形阵的定位精度,应尽量提高浮标的测向精度和浮标位置精度;使用中应根据浮标性能和实际使用需求选取合理的布阵间距。     

混凝土养护期间HRB400钢筋钝化行为研究

为了研究HRB400钢筋在模拟养护阶段混凝土孔隙液中表面钝化膜的生长过程,采用3种电化学测试技术(开路电位、电化学阻抗谱、动电位极化曲线)研究钢筋表面钝化膜的性能随着浸泡时间的变化特征,此外通过XPS对稳定钝化膜的成分与结构进行分析。结果表明,同传统钢筋材料一样,HRB400钢筋在模拟混凝土养护条件的溶液中展现出良好的耐蚀性能,浸泡5 d后便能够生成稳定钝化膜。XPS分析发现钢筋钝化膜为双层结构,内层以二价铁离子化合物为主,外层主要由三价铁离子化合物组成。     

Rational Filters for Passive Depth from Defocus

A fundamental problem in depth from defocus is the measurement of relative defocus between images. The performance of previously proposed focus operators are inevitably sensitive to the frequency spectra of local scene textures. As a result, focus operators such as the Laplacian of Gaussian result in poor depth estimates. An alternative is to use large filter banks that densely sample the frequency space. Though this approach can result in better depth accuracy, it sacrifices the computational efficiency that depth from defocus offers over stereo and structure from motion. We propose a class of broadband operators that, when used together, provide invariance to scene texture and produce accurate and dense depth maps. Since the operators are broadband, a small number of them are sufficient for depth estimation of scenes with complex textural properties. In addition, a depth confidence measure is derived that can be computed from the outputs of the operators. This confidence measure permits further refinement of computed depth maps. Experiments are conducted on both synthetic and real scenes to evaluate the performance of the proposed operators. The depth detection gain error is less than 1%, irrespective of texture frequency. Depth accuracy is found to be 0.51.2% of the distance of the object from the imaging optics.     

基于自抗扰技术的高超声速飞行器控制系统设计

高超声速飞行器在飞行过程中超燃冲压发动机对攻角及侧滑角有较严格的要求,为实现对攻角及侧滑角的精确控制,文章采用自抗扰控制技术设计了高超声速飞行器的攻角自动驾驶仪;首先建立高超声速飞行器控制系统的数学模型,然后采用扩张状态观测器对受扰对象的状态和干扰进行观测,并对状态误差采用非线性反馈,对观测的干扰进行补偿,从而实现对干扰的快速抑制和对指令的精确跟踪,最后仿真表明所设计的自动驾驶仪满足性能要求,验证了该方法的正确性。     

AES加密算法的无钥匙进入系统

市场上车门无钥匙进入(Passive Keyless Entry,PKE)系统成本高、种类少、应用灵活度低,大部分汽车无法配备.本文在AES加密算法的基础上,提出了一种类似于滚动加密算法(KEELOQ)的通信安全协议,并应用于无钥匙进入系统,既降低了成本,又保证了通信安全,且更具灵活性.     

ISS feedback control redesign for continuous stirred tank reactors

In this paper a new nonlinear feedback control law for continuous stirred tank reactors, obtained by exact Input/Output (I/O) linearization and Sontag's input‐to‐state stability feedback control redesign methods, is studied. By the new feedback control law, a significant attenuation of the disturbance effect is guaranteed, with evident improvement with respect to control laws obtained by the exact I/O linearization method. The performed simulations validate the theoretical results. Copyright © 2010 John Wiley & Sons, Ltd.