H.264跳帧转码中帧间模式选择和运动估计快速算法*

为了解决在H.264跳帧转码中,简单地重用从输入码流中获取的编码信息得到的视频质量非常不理想的问题。针对宏块的运动特征,引入运动尺度因子,提出快速帧间模式选择算法和新的运动矢量合成算法,在提高视频质量的同时大大降低了算法复杂度,并提出基于双阈值的自适应运动矢量修正算法,可以有效减少当获得最佳运动矢量后进行修正的冗余运算量。实验证明,此算法具有更强的鲁棒性和更广泛的适用性,在转码后的视频质量和转码速度方面都达到了很好的效果。     

多弧离子镀Ti-N镀膜的扩散屏障作用

设计了３种复合镀层系，研究了多弧离子镀Ｔｉ－Ｎ镀膜对Ａｌ，Ｎｉ，Ｃｏ的扩散屏障作用及Ｔｉ－Ｎ镀膜在１０００和１１００℃长期时效时的热稳定化结果表明，在１０００℃以下时效时，Ｔｉ－Ｎ镀膜稳定性良好，并可有效地阻止Ａｌ向基材扩散，可减缓、阻止Ｎｉ，Ｃｏ在ＣｏＣｒＡｌＴａＹ涂层与基体间的互扩散行为；在１１００℃时效时，Ｔｉ－Ｎ镀膜未分解，也不与基材及ＣｏＣｒＡｌＴａＹ涂层间发生互扩散，但组织形态由薄膜变为颗粒状，颗粒状Ｔｉ－Ｎ无法阻止Ｎｉ，Ｃｏ在ＣｏＣｒＡｌＴａＹ涂层与基材间的互扩散．     

Deformation and pore formation mechanism under tensile loading in isotactic polypropylene

Four different polypropylene (PP) samples were prepared through isothermally crystallizing at 0 °C (PP‐Q), 80 °C (PP‐80), 100 °C (PP‐100) and 120 °C (PP‐120). The results of differential scanning calorimetry, wide‐angle X‐ray diffraction, polarized light microscopy and tensile testing indicate that the spherulite structure gradually improves with increasing isothermal crystallization temperature. Meanwhile, the interface between spherulites becomes more obvious due to the larger dimension and the higher strength of spherulites. Therefore, the trend of interfacial debonding during stretching is enhanced distinctly. In addition, based on the structural characterization of samples at different draw ratios, two completely distinct morphological changes are demonstrated. There are no defects generated after longitudinal stretching within PP‐Q, because intra‐spherulitic deformation predominates, which is caused by the imperfect spherulites of PP‐Q. As a result, no microporous structure is produced after sequential biaxial stretching. And the improvement of the crystalline structure makes interfacial debonding more likely to occur. Therefore, fully developed crazes and cracks disperse between microfibril structures after longitudinal stretching. Furthermore, numerous microporous structures are produced through debonding of fully developed crazes and cracks after sequential biaxial stretching. Meanwhile, the quantity, dimension and uniformity of the microporous structures and the porosity are gradually improved. © 2017 Society of Chemical Industry     

沸石催化剂内液相交互扩散系数的测定

采用简单实用的试验方法研究了苯和异丙苯在沸石内的交互扩散情况,通过测定不同时间点的扩散质的浓度,利用适宜的数学模型和最小二乘法关联出两种体系中各扩散质在沸石催化剂内的交互扩散系数。可以为苯烷基化反应的工业模拟提供重要的基础数据。     

Solidified structure of thin-walled titanium parts by vertical centrifugal casting

The solidified structure of the thin-walled and complicated Ti-6Al-4V castings produced by the vertical centrifugal casting process was studied in the present work. The results show that the wall thickness of the section is featured with homogeneously distributed fine equiaxial grains, compared with the microstructure of the thick-walled section. The grain size of the castings has a tendency to decrease gradually with the increasing of the centrifugal radius. The inter-lamellar space in thick-walled casting parts is bigger than that of the thin-walled parts, and the profile of inter-lamellar space is not susceptible to the centrifugal radius.     

φ101牙轮钻头设计与加工工艺

详细介绍了φ104牙轮钻头的设计计算过程和加工工艺。     

基于互关联后继树的多时间序列关联模式挖掘

时间序列是现实生活中常见的数据形式之一，在时间序列中发现频繁模式是分析时间序列变化规律的一项重要任务．提出基于互关联后继树的多时间序列关联模式挖掘算法．该算法首先用Allen逻辑位置关系来描述序列状态关系，根据这些关系在时间窗口内顺序或并行出现情况，获得一个由这些关系组成的特殊序列．在此基础上提出了一个基于互关联后继树的新型挖掘模型，实现了序列间关联模式的挖掘．与其他方法相比，该算法简单、直观，而且整个挖掘过程不需要生成候选模式，大大提高挖掘效率．     

Event-Triggered Sliding Mode Control for Trajectory Tracking of Nonlinear Systems

In this paper, an event-triggered sliding mode control approach for trajectory tracking problem of nonlinear input affine system with disturbance has been proposed. A second order robotic manipulator system has been modeled into a general nonlinear input affine system. Initially, the global asymptotic stability is ensured with conventional periodic sampling approach for reference trajectory tracking. Then the proposed approach of event-triggered sliding mode control is discussed which guarantees semi-global uniform ultimate boundedness. The proposed control approach guarantees non-accumulation of control updates ensuring lower bounds on inter-event triggering instants avoiding Zeno behavior in presence of the disturbance. The system shows better performance in terms of reduced control updates, ensures system stability which further guarantees optimization of resource usage and cost. The simulation results are provided for validation of proposed methodology for tracking problem by a robotic manipulator. The number of aperiodic control updates is found to be approximately 44% and 61% in the presence of constant and time-varying disturbances respectively.     

An integrated mathematical model for solving dynamic cell formation problem considering operator assignment and inter/intra cell layouts

The aim of this paper is to present an integrated mathematical model to solve the dynamic cell formation problem considering operator assignment and inter/intra cell layouts problems with machine duplication, simultaneously. The proposed model includes three objectives which the first objective seeks to minimize inter/intra cell part movements and machine relocation, the second objective minimizes machine and operator related costs and the third objective maximizes consecutive forward flows ratio. In order to validate the proposed model, a numerical example is presented and solved by the sum weighted method. Due to NP-hardness of the model, two meta-heuristics namely multi-objective simulated annealing (MOSA) and multi-objective vibration damping optimization (MOVDO) present to solve the proposed model. Finally, two algorithms have been compared using multi-objective criteria.