一种新的基于梯度方向直方图的图像配准方法*

构建了一种新的局部梯度方向直方图,同时定义了特征点的主方向,从而提出了一种具有旋转不变性的图像配准算法.首先采用高斯加权求模技术对特征点邻域内的像素的梯度作直方图统计,确定出具有旋转不变性和抗噪性的特征点主方向;然后用主方向作角度直方图统计,确定待配准图像之间的旋转角度.根据得到的特征点信息及旋转角度定义了特征点对互信息匹配准则,这样使得新配准算法对于图像间旋转角度的范围没有限制,获得了良好的配准效果.     

热力耦合作用下Al-2.8%Cu-1.35%Li-0.11%Zr合金析出相演化和力学性能

通过TEM、HAADF-STEM和室温拉伸实验开展Al-2.8%Cu-1.35%Li-0.3%Mn-0.11%Zr合金在人工时效和蠕变时效状态下的析出相演化规律和力学性能研究。结果表明,160 ℃时效条件下,人工时效和160 MPa应力时效过程中合金中析出相数量均随时效时间的延长而增多,相同时效时间条件下应力时效状态合金T₁相数量较多,但其平均直径减小了约5~15 nm。这主要是因为外加应力增加了合金中的位错密度从而促进析出相析出。T₁相在时效析出过程中并未受外加应力的影响而沿某个方向择优析出,无明显的应力位向效应,这可能与T₁相具有更大的惯习平面变体上的形核与临界应力值有关。相比于人工时效,应力时效后合金的室温屈服强度和抗拉强度均增加,且在时效初期对屈服强度效果更为显著。      

论研究型大学的办学取向

研究型大学，是创办世界一流大学的必由之路。本文试图从教育的综合性、科研的前沿性、管理的科学性、环境的学术性等四个维度等来阐述大学向研究型迈进所必须作出的取向选择，以此为研究型大学的创建提供一种新的思路。     

一种新的Kossel定向方法

本文提出一种新的Kossel定向方法。它只要求测出透射Kossel花样上的三个Kossel线交点之间的距离就能定向,从而减少了误差的来源,提高了定向精度。通常的透射Kossel照片定向误差为σ=±0.3°     

TiAl 合金中的γ→α析出转变行为

研究了Ti-48Al和Ti-48Al—0．8B合金中的γ→α析出转变，分析了α析出相的生长形态、晶体学特征、生长动力学及α／γ相界面结构。结果显示α相从γ相中析出有两种方式：一种是从γ晶粒内沿{111}，晶面以片状形貌析出，且α相与γ基体保持共格位向关系；另一种则是在γ晶界上通过不连续析出转变，以不规则的块状形貌析出，并向着晶界一侧与之无位向关系的γ晶粒内生长。添加0．8％(摩尔分数)B能显著降低γ晶粒内片状α析出相的形核率，并抑制α相生长。HREM分析表明：片状α相是在γ相的堆垛层错上形核，并通过“台阶-凸起-扭折”机制生长；α／γ相界面上复杂层错的存在及台阶形核率低是片状α相沿厚度方向生长缓慢的主要原因。     

定向凝固AZ31镁合金晶粒取向及力学性能研究

采用自行设计的定向凝固装置制备了AZ31镁合金铸件,通过金相观察、XRD分析和室温压缩试验,研究定向凝固工艺对AZ31镁合金晶粒取向和常温力学性能的影响。结果表明:定向凝固制备的AZ31镁合金铸件具有柱状晶组织,第二相呈球状弥散分布于晶粒内部。由于温度梯度的影响,晶体规律性地定向生长,呈现较明显的[1010]择优取向。该铸件在常温力学性能和塑性成形性能上表现出各向异性的特点。     

工艺条件对YBCO厚膜基带晶粒取向的影响

用Ｘ射线方法研究了平行于基带表面的Ｎｉ（２０Ｏ），Ｎｉ（１１１），ＮｉＯ（２００）和ＮｉＯ（１１１）晶面的取向分数Ｗ。结果表明，随预热处理温度的提高，虽然Ｗ_（ＮｉＯ（２００））也会随之提高，但是区域重加热处理对提高Ｗ_（ＮｉＯ（２００））起着最重要的作用。９００℃预热处理之后，在１１００℃进行区域重加热可使Ｗ_（ＮｉＯ（２００））提高到０．９９以上。     

Characterization of molecular orientation in injection–stretch–blow‐molded poly(ethylene terephthalate) bottles by means of external reflection infrared spectroscopy

The molecular orientation at the outer surface of injection–stretch–blow‐molded bottles made from poly(ethylene terephthalate) was characterized and quantified by means of front‐surface reflection infrared spectroscopy based on a method developed previously. Results were obtained for two different bottle shapes (cylindrical and rectangular) molded at different injection mold temperatures (16, 38, and 60°C). For the cylindrical bottles, the preferred molecular chain orientation was found to be in the axial direction, with the Hermans orientation function near 0.3 for all three mold temperatures. For the less symmetrical rectangular bottles, a significant difference was observed between the large and small faces. For the large face, the orientation was mainly in the hoop direction; the Hermans orientation function was in the range of 0.3–0.5 and was essentially the same at all mold temperatures and positions along the bottle height. For the small face, on the other hand, the preferred orientation changed from the hoop direction near the bottom to the axial direction near the top, and the variation was more pronounced at lower mold temperatures. The utility of the front‐surface reflection technique was clearly demonstrated. It was also applied, with the use of an infrared microscope, to examine the orientation gradient across the wall thickness. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1319–1327, 2007     

Direct evidence for chain orientation in poly(acetylene)

Two conflicting structural models (platelet and fibril) have been proposed in the literature for pristine cis-poly(acetylene). The respective models have separate, distinct implications for the chemical, physical and electrical properties of the material, in particular, the cis-trans isomerization, doping and conduction mechanisms. Luttinger-type cis-poly(acetylene) was prepared and studied in the transmission electron microscope (TEM) by low-dose conventional imaging, in dark-field mode and by electron diffraction. Thin ‘films’ of the material were shown to consist of fibrillar nets, having fibrils of diameter 5–25 nm. Combined electron diffraction and dark-field observations in the TEM indicated the structural arrangement within the fibrils as that having polymer molecular chains aligned parallel to fibril axes.     

将开滦建成国内一流煤炭洗选加工基地的构想与实施

着重对开滦煤炭洗选加工的现状进行了分析和研究 ,总结了目前选煤系统存在的问题与差距 ,论证了开滦建设一流煤炭洗选加工基地的定位、主要内容 ,结合实际情况提出了实施建议。