The anti-reflective algebra: structural and computational analysis with application to image deblurring and denoising

Anti-reflective (AR) boundary conditions (BC) have been introduced recently in connection with fast deblurring algorithms, both in the case of signals and images. Here we extend such BCs to d dimensions (d ≥ 1) and we study in detail the algebra induced by the AR-BCs, with strongly symmetric point spread functions (PSF), both from a structural and computational point of view. The use of the re-blurring idea and the computational features of the AR-algebra allow us to apply Tikhonov-like techniques within O(n ^d log(n)) arithmetic operations, where n ^d is the number of pixels of the reconstructed object. Extensive numerical experimentation concerning 2D images and strongly symmetric PSFs confirms the effectiveness of our proposal.      

一种基于H.264/AVC的快速帧间模式选择算法

为了解决帧间模式选择计算量大的问题,提出了一种快速算法。算法利用编码模式的利用率信息和时空相关性来预先判定当前宏块最可能的编码模式,从而大大加快了模式选择的过程。算法缩小了候选模式的范围,并采用阈值来提高预测准确度。仿真结果表明,该算法在编码质量只有轻微下降的情况下明显降低了计算复杂度。     

快速傅里叶变换在轧辊偏心补偿控制中的应用

描述了轧辊偏心信号的特点.介绍了基于快速傅里叶变换的轧辊偏心补偿控制策略,并给出了实施效果.     

Turbo spin-echo sequences in magnetic resonance imaging of the brain: Physics and applications

Fast SE imaging provides considerable measure time reduction, high signal-to-noise ratios as well as similar contrast behavior compared to conventional SE sequences. Besides TR and TE_eff, echo train length (ETL), interecho time , and-space trajectory determine image contrast and image quality in fast SE sequences. True proton density contrast (CSF hypointense) and not too strong T2 contrast are essential requirements in routine brain MRI. A Turbo SE sequence with very short echo train length (ETL=3), short TE_eff and short interecho time (17 ms), and TR=2000 ms was selected for proton density contrast; a Turbo SE sequence with ETL=7, TE_eff=90 ms, =22 ms, and TR=3250 ms was selected for T₂-weighted images. Using both single-echo Turbo SE sequences yielded 50% measure time reduction compared to the conventional SE technique. Conventional SE and optimized Turbo SE sequences were compared in 150 patients resulting in very similar signal and contrast behavior. Furthermore, reduced flow artifacts in proton density—and especially in T₂-weighted Turbo SE images—and better contrast of high-intensity lesions in proton density-weighted Turbo SE images were found. Slightly reduced edge sharpness—mainly in T₂-weighted Turbo SE images—did not reduce diagnostic reliability. Differences between conventional and Turbo SE images concerning image contrast and quality are explained regarding special features of fast SE technique.Address for correspondence: Institut für Röntgendiagnostik, Klinikum der Universität Regensburg, Franz-Josef-Strauß-Allee 11, 93042 Regensburg, Germany. Additional reprints of this chapter may be obtained from the Reprints Department, Chapman & Hall, One Venn Plaza, New York, NY 10119.     

Nonlinear cascade control of an electro-hydraulic actuator with large payload variation

Electro-hydraulic actuators have been widely used in industrial production, but the unknown variable payload seriously affects its position control accuracy. Therefore, a radial basis function neural network disturbance observer is designed to estimate the lumped disturbance force through strong online learning ability in the absence of force sensor. Besides, a nonlinear cascade controller with double loop structure is proposed in this paper. A global fast terminal sliding mode control method is firstly applied in the outer loop position system, which can eliminate chattering and improve convergence speed comparing to traditional sliding mode control. The inner loop force system adopts a backstepping control method to calculate the actual input of the whole system. Theoretical analysis indicates that the proposed controller is stable even if existing time-variant disturbance. Moreover, three comparative controllers are designed and tested in both simulations and experiments. Comparative results show that the developed method has absolute average errors of 1.14 and 0.49 mm in different position tracking, which means more satisfactory tracking performance compared to the contrast controllers.     

Implicit discrete-time fast terminal sliding mode control with disturbance compensation

In this paper, an implicit discrete-time fast terminal sliding mode (DFTSM) control with disturbance compensation is designed and analyzed for uncertain high-order systems. First, a recursive discrete sliding surface is constructed based on implicit Euler technique, which can completely eliminate discretization chattering so as to significantly reduce the boundary layer of sliding mode motion. With the help of a high-order disturbance compensator, the accuracy limitation of implicit DFTSM control systems is overcome by increasing the order of sliding mode. Then the finite-time convergence of implicit DFTSM is proved for the first time, and the influence relationship of control parameters on the convergence speed and control accuracy of the algorithm is established. Finally, two numerical examples are provided to demonstrate the effectiveness and superiority of the proposed design approach.     

快/慢烤试验中复合推进剂内部温度场的分布

为了研究不同烤燃条件下复合推进剂(PBT/HMX/Al/AP/BU)的响应特性,采用DSC研究了复合推进剂及单组分的热分解特性。复合推进剂的初始分解温度为187.27℃,单组分中BU初始分解温度最低,为192.95℃,表明复合推进剂的热分解过程是从BU开始;分别测量了在快/慢烤试验中,复合推进剂内部温度的变化。结果表明:1)快烤试验中,样品内部温度分布极不均匀。点火90 s后,样品发生反应,此时样品中心的温度为85℃,钢管端盖破裂,样品发生燃烧反应。2)慢烤试验中,样品内部温度分布均匀,几乎无温度差,样品发生反应时,样品内部温度与环境温度均为133℃,试验后样品钢管完全破碎,样品发生了爆轰。由此可见,慢烤试验中,由于样品内部温度分布均匀,发生反应时,大部分样品都处于临界反应温度,一旦激发,破坏效应比快烤试验更严重。     

基于单片机的高精度快速积分型AD转换器

针对现有积分型AD转换器存在转换速率较低的问题,提出了一种基于单片机的高精度快速积分型AD转换器的设计方案,详细介绍了AD转换的实现过程。该转换器采用单片机产生各种控制信号,保证了测量过程的精确同步,提高了AD测量结果的稳定性,最快转换速度可达500次/s。实际应用表明,该转换器转换速度快,测量精度高,达到了预期效果。     

Nonsingular fast terminal sliding‐mode control for nonlinear dynamical systems

This paper investigates fast finite‐time control of nonlinear dynamics using terminal sliding‐mode (TSM) scheme. Some new norms of fast TSM strategies are proposed, and a faster convergence rate is established in comparison with the conventional fast TSM. A novel concept of nonsingular fast TSM, which is able to avoid the possible singularity during the control phase, is adopted in the robust high‐precision control of uncertain nonlinear systems. Numerical simulation on a two‐link rigid robot manipulator demonstrates the effectiveness of the proposed algorithm. Copyright © 2010 John Wiley & Sons, Ltd.