Comparative wear performance of titanium based coatings for automotive applications using exhaust gas recirculation

This paper reports tribological characterization of titanium based coatings ion bonded on steel balls for automotive applications using exhaust gas recirculation (EGR). It is well known that lubricating oil drawn from EGR operated engine is contaminated with soot and higher amounts of wear debris compared to non-EGR operated engine. In this study, steel balls coated with TiN, TiAlN and TiCN are investigated in both fresh lubricating oil and EGR stressed oil for a comparative assessment of their wear characteristics in two mediums. Normal load was applied on the samples, tested against a rotating cast iron disk, simulating ring-liner interaction. In each experiment, about one quarter of disk was dipped in the oil (a) to ensure the presence of a thin oil film on the disk-ball interface during the experiment, and (b) to avoid exposure of the worn surface to atmospheric air. The results reveal that the wear rates of the coatings based on the change in the scar diameters of the samples, tested in EGR oil was 2-4 times higher than that of fresh lubricating oil. It was found that despite lowest hardness, TiN coated samples showed smaller scar diameters than TiAlN and TiCN coated samples in both lubricating oil environments. A simple geometric model was used to calculate the thickness of the coating removed as a function of the test duration. Results show that TiN coatings last for 120 min in fresh oil as compared to 30 min in the EGR oil under normal loading, whereas TiAlN and TiCN coating last for 60 and 30 min respectively in fresh oil and wear out in 15 min in EGR oil.     

基于ProCAST的消失模铸造工艺的数值模拟研究

运用ProAST软件对链轮铸钢件的消失模铸造工艺进行了充型和凝固过程的数值模拟评价,分析了缺陷产生的原因,对铸造工艺进行了优化,并结合实际生产情况,给出了影响消失模铸造的六大基本因素。     

碳对马氏体钢显微组织和力学性能的影响

通过固定其它元素的含量，调整碳含量的方式，研究了碳含量对马氏体钢显微组织和力学性能的影响。结果表明，随碳含量增加，马氏体钢的硬度和抗拉强度提高，但冲击韧度下降。     

钛合金髋关节铸造工艺CAD及模拟验证

设计了钛舍金髋关节的金属型离心铸造工艺方案，并对其充型过程和凝固过程进行了数值模拟验证，得到了较合理的铸造工艺方案，实际浇注表明，工艺是合理的。首先针对钛舍金髋关节的结构特点进行了分体模数计算，在此基础上，根据钛舍金的铸造工艺特点进行了铸造工艺设计，即将钛舍金髋关节分5个部分进行补缩，浇注速度要大，浇注时间要短，真空度要高，浇注温度大于等于1760℃。进行工艺优化后，数值模拟结果和实际浇注表明，设计可以满足要求。     

碳对马氏体钢显微组织和力学性能的影响

通过固定其它元素的含量,调整碳含量的方式,研究了碳含量对马氏体钢显微组织和力学性能的影响。结果表明,随碳含量增加,马氏体钢的硬度和抗拉强度提高,但冲击韧度下降。     

局部不变特征点的精度指标

目的 作为计算机视觉的热门研究方向,局部不变特征算法的发展已趋于成熟、稳定,然而目前几乎所有特征点提取算法都没有给出特征点的精度指标.针对这一缺陷,提出一种特征点精度指标-特征点波动区间.方法 性质稳定的点在干扰条件下仍具有较好的精度,即小范围的波动区间,因此,以当前最热门的SIFT(scale-invariant feature transform)特征点为例,在图像加入噪声,发生光照变换,发生模糊变换以及同时进行噪声、光照及模糊处理这四种情况下分别分析同一算法提取的不同特征点的波动情况,进而得到不同特征点的波动区间.结果 实验得到16个稳定检出特征点,其中点2,3,4,11,13这5个点可以在不同干扰条件下的波动范围都较小,而点2则只在模糊条件下波动较小,在其余干扰下波动较大.特征点虽然已经过特征提取,但仍具有不同的波动区间,其优劣也不尽相同.不同的特征点的波动区间并不相同,但仍有一部分特征点在不同干扰条件下均保持较高的提取精度.结论 波动区间能很好地表征每个特征点的提取精度.由于此前只有针对特征点算法的评价指标,而没有针对特征点自身性质的评价方法,因此本文提出的特征点波动区间将为诸如设备标定、视觉测量、精简特征库等相关后续工作打下良好基础.     

Combined salience based person re-identification

Human eye perceives an object as the entity with global information and local information. Human salience is distinctive local information in matching pedestrians across disjoint camera views, and matching on overall foreground guarantees reliable and robust identification. In this paper, we propose a strategy for the matching of mean salience to identify pedestrians. Also, we consider that person re-identification based on the local single directional matching suffers from the variations of pose, illumination and overlapping, and propose a global bi-directional matching to solve the challenging problems of person re-identification. Furthermore, our matching of mean salience is tightly combined with the global bi-directional matching. Patch matching is utilized to handle the misalignment problem in pedestrian images. We test our feature and matching approaches in person re-identification scenario. Experimental results demonstrate that the mean salience and the global bi-directional matching have promising discriminative capability in comparison with other ones.     

一种基于局部加权回归的分类方法

分类是数据挖掘和数据分析中最有应用价值的技术之一。传统的积极学习方法需要预先对模型空间进行假设,并且没有充分考虑到实例之间的相关性,其泛化能力将会受到一定程度的影响。针对上述问题,提出了一种基于新型映射关系的局部加权回归方法 MLWR。该算法首先找出测试样本在训练集中的近邻样本,然后建立测试样本和近邻样本的回归函数,根据建立的回归模型和近邻样本的标签,计算得到测试样本的标签。实验与当前流行的多种分类方法在UCI的9个数据集上进行测试。实验结果表明我们的方法能有效地提高分类精度,对较大样本数据也有较好的适用性。     

Novel neural network modeling method and applications

Neural networks play an important role for designing the parametric model of electromagnetic structures. The current neural network methods are unfit for a circuit model with many input variables because it is costly to extract a large number of the training data and test data to complete the highly nonlinear mapping approximation. This article proposes a new neural network modeling method—the multidimensional neural network model, which can be used to solve the issue of multivariable radiofrequency and microwave passive device modeling. The entire multidimensional neural network modeling problem is simplified into a set of neural network submodels through decomposition method. Then the submodels are combined into an equivalent model, and the final entire model is produced through the neural‐network mapping model developed with the submodels and equivalent model. A microstrip hairpin filter model is developed using the proposed method. The simulation results show the correctness and the effectivity of the proposed method. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:769–779, 2015.     

Mode-selective dynamic light scattering: theory versus experimental realization

We present a quantitative experimental comparison of fiber-based, single- and few-mode dynamic light scattering with the classical pinhole-detection optics. The recently presented theory of mode-selective dynamic light scattering [Appl. Opt. 32, 2860 (1993)] predicts a collection efficiency and a signal-tobaseline ratio superior to that of a classical pinhole setup. These predictions are confirmed by our experiments. Using single-mode optical fibers with different cutoff wavelengths and commercially available mechanical components, we have constructed a mode-selective detection optics in a simple and compact dynamic light-scattering spectrometer that permits an optimal compromise between signal intensity and dynamical resolution.