Over-relaxation effect of deformed austenite on ageing behavior of an Nb-bearing microalloyed steel

The ageing behavior of an Nb-bearing microalloyed steel at 525℃ was investigated by thermo-simulation test, hardness measurements and transmission electron microscopy (TEM). Prior to ageing, the steel was deformed in austenite zone followed by a long relaxation. Experimental results indicate that the hardness decreases gradually in the initial stage until ageing for 120 min, and then increases continuously until 1200 min. The coarsened precipitates (>10 nm) formed in deformed austenite remain nearly unchanged in size, even after ageing for long time, while the further precipitates, which nucleate in a phase, contribute to the increasing of hardness. By comparison, the undeformed samples in austenite subjected to the same ageing process display a very similar hardness change trend to that of over-relaxation ones and have higher hardness values at each corresponding period.

On Over-Relaxed Proximal Point Algorithms for Generalized Nonlinear Operator Equation with (A,η,m)-Monotonicity Framework

In this paper, a new class of over-relaxed proximal point algorithms for solving nonlinear operator equations with (A,η,m)-monotonicity framework in Hilbert spaces is introduced and studied. Further, by using the generalized resolvent operator technique associated with the (A,η,m)-monotone operators, the approximation solvability of the operator equation problems and the convergence of iterative sequences generated by the algorithm are discussed. Our results improve and generalize the corresponding results in the literature.

基于全局概率密度搜索的快速目标跟踪

为了解决均值迁移目标跟踪算法中跟踪窗口对局部概率密度模式敏感的问题,该文提出一种基于全局概率密度搜索的目标跟踪策略。根据目标尺度设定一组从大到小排列的带宽序列,并依次根据每个带宽进行均值迁移迭代收敛,利用大带宽的平滑作用避开局部概率模式的干扰;依靠小带宽进行精确定位,最终收敛到真实目标区域。为了提高均值迁移的收敛速度,引入了Over-Relaxed优化策略加速迭代过程。在边界优化算法的收敛条件约束下,根据采用Over-Relaxed策略前后相关系数的变化,自适应地调整学习率。实验结果表明全局概率密度搜索能够有效地跟踪快速运动的目标,并且当目标短暂丢失时也有一定的恢复能力;Over-Relaxed策略也能显著的提高收敛步长,减少迭代次数。

Hybrid Methods for Computing the Streamfunction and Velocity Potential for Complex Flow Fields over Mesoscale Domains

Three types of previously used numerical methods are revisited for computing the streamfunctionψand velocity potentialχfrom the horizontal velocity v in limited domains.The first type,called the SOR-based method,uses a classical successive over-relaxation(SOR)scheme to computeψ(orχ)first with an arbitrary boundary condition(BC)and thenχ(orψ)with the BC derived from v.The second type,called the spectral method,uses spectral formulations to construct the inner part of(ψ,χ)-the inversion of(vorticity,divergence)with a homogeneous BC,and then the remaining harmonic part of(ψ,χ)with BCs from v.The third type,called the integral method,uses integral formulas to compute the internally induced(ψ,χ)-the inversion of domain-internal(vorticity,divergence)using the free-space Greenꞌs function without BCs and then the remaining harmonicψ(orχ)with BCs from v minus the internally-induced part.Although these methods have previously been successfully applied to flows in large-scale and synoptic-scale domains,their accuracy is compromised when applied to complex flows over mesoscale domains,as shown in this paper.To resolve this problem,two hybrid approaches,the integral-SOR method and the integral-spectral method,are developed by combining the first step of the integral method with the second step adopted from the SOR-based and spectral methods,respectively.Upon testing these methods on real-case complex flows,the integral-SOR method is significantly more accurate than the integral-spectral method,noting that the latter is still generally more accurate than the three previously-used methods.The integral-SOR method is recommended for future applications and diagnostic studies of complex flows.

Calibrating Remotely Sensed Ocean Chlorophyll Data: An Application of the Blending Technique in Three Dimensions (3D)

In this article, the extension to three dimensions (3D) of the blending technique that has been widely used in two dimensions (2D) to calibrate ocean chlorophyll is presented. The results thus obtained revealed a very high degree of efficiency when predicting observed values of ocean chlorophyll. The mean squared difference between the predicted and observed values of ocean chlorophyll when 3D technique was used fell far below the tolerance level which was set to the difference between satellite and observed in-situ values. The resulting blended field did not only provide better predictions of the in situ observations in areas where bottle samples cannot be obtained but also provided a smooth variation of the distribution of ocean chlorophyll throughout the year. An added advantage is its computational efficiency since data that would have been treated at least four times would be treated only once. With the advent of these results, it is believed that the modelling of the ocean life cycle will become more realistic.

Application of the Level-Set Model with Constraints in Image Segmentation

We proposeand analyze a constrained level-set method forsemi-automatic image segmentation.Our level-set model with constraints on the level-set function enables us to specify which parts of the image lie inside respectively outside the segmented objects.Such a-priori information can be expressed in terms of upper and lower constraints prescribed for the level-set function.Constraints have the same conceptual meaning as initial seeds of the popular graph-cuts based meth-ods for image segmentation.A numerical approximation scheme is based on the complementary-finite volumes method combined with the Projected successive over-relaxation method adopted for solving constrained linear complementarity prob-lems.The advantage of the constrained level-set method is demonstrated on several artificial images as well as on cardiac MRI data.