基于顺序形态变换的生物芯片图像网格化

生物芯片图像网格化是对由生物芯片扫描得到的荧光成像中的信号(Foreground)和背景(Background)进行划分,以便提取各点的吸光度值、面积和吸光度比等荧光点的数据。网格化的准确与否决定了数据提取的正确性。提出了一种运用顺序形态变换理论实现生物芯片荧光图像网格化的方法,通过对百分位值在0~1之间的顺序形态进行变换,可实现像素灰度的极小值、中间值等多刻度值的灰度取值运算。理论分析表明,该算法能够识别信号与背景的边界,可去除噪声等非边界信息,能判断信号区域,可确定荧光点的边界和范围,可实现荧光点阵图像的网格化。试验结果表明,该算法对不同信噪比的荧光图像来说有很强的适应性,可用于高密度生物芯片图像的处理。     

激光网格化淬火表面渗硫/纳米微粒复合层的摩擦学性能研究

利用MFT-R4000摩擦磨损试验机考察了激光网格化淬火表面渗硫复合层(简称SLD层)和激光网格化淬火表面渗硫/纳米微粒复合层(简称NLD层)在不同试验载荷时的减摩抗磨性能,利用SEM和XPS分析了不同试验条件下磨损表面形貌和所含元素及其化学价态.结果表明:NLD层不仅在重载荷下的减摩性能比SLD层的优异,其在干摩擦条件下的摩擦系数仅为0.075左右,而且在较低试验载荷下具有很长的使用寿命.磨损表面元素分析发现S元素以硫化物和硫酸盐形式存在,但没有发现Si元素,这表明磨损表面形成了主要由硫化物、硫酸盐和氧化物组成的摩擦化学反应膜,而n-SiO2颗粒在摩擦表面可能起到了"微纳滚珠"的作用.     

液晶等各向异性物体偏振光学图案的格栅计算方法和解析计算方法

本文推广获得了计算偏振光学图案的格栅方法,指出该方法可以处理具有任意指向矢排布的各向异性物体。进一步用色块显示法可获得层次丰富的理论图案。通过理论计算和安验观察,验证了运用偏光显微法可以鉴别液晶缺陷的强度与符号,这将有助于从微观水平上认识向列型液晶的纹影织构。等θ条件下,格栅方法可以过渡到解析方法,在单色光和多色光照射下的计算公式均已给出。     

基于球形颗粒几何排列的离散元试样高效生成方法

在球体离散元数值模拟中,颗粒的初始排列状态是影响计算效率和计算结果的重要环节。本文采用前进面几何构造算法,提出了一种基于网格搜索的球形颗粒随机排列高效算法。通过求解空间三边方程,满足了粒径设置的任意大小的颗粒依次置入前进面的外侧,并与构成前进面的三个颗粒相互接触。为获得高体积分数的颗粒簇,该算法允许颗粒改变其粒径大小。采用颗粒网格化方法可以简化前进面的搜索,并由此提高排列效率。通过计算平均配位数、体积分数和二阶结构张量的特征值,对不同粒径比下得到的立方体试样进行了分析,得到试样配位数及体积分数均随着粒径比的增大而增大,且得到的试样为各向同性。此外,空间网格的大小和初始颗粒的生成点对随机排列的效率均会产生显著的影响。最后,对非规则铁路道砟进行了精细构造及压碎模拟,发现DEM模拟得到的应力-应变曲线与试验结果基本吻合,验证了该算法得到的颗粒试样在模拟道砟裂纹起裂、扩展等过程的有效性。     

Reduced aliasing artifacts using shaking projection k-space sampling trajectory

Radial imaging techniques, such as projection-reconstruction （PR）, are used in magnetic resonance imaging （MRI） for dynamic imaging, angiography, and short-T2 imaging. They are less sensitive to flow and motion artifacts, and support fast imaging with short echo times. However, aliasing and streaking artifacts are two main sources which degrade radial imaging quality. For a given fixed number of k-space projections, data distributions along radial and angular directions will influence the level of aliasing and streaking artifacts. Conventional radial k-space sampling trajectory introduces an aliasing artifact at the first principal ring of point spread function （PSF）. In this paper, a shaking projection （SP） k-space sampling trajectory was proposed to reduce aliasing artifacts in MR images. SP sampling trajectory shifts the projection alternately along the k-space center, which separates k-space data in the azimuthal direction. Simulations based on conventional and SP sampling trajectories were compared with the same number projections. A significant reduction of aliasing artifacts was observed using the SP sampling trajectory. These two trajectories were also compared with different sampling frequencies. ASP trajectory has the same aliasing character when using half sampling frequency （or half data） for reconstruction. SNR comparisons with different white noise levels show that these two trajectories have the same SNR character. In conclusion, the SP trajectory can reduce the aliasing artifact without decreasing SNR and also provide a way for undersampling recon- struction. Furthermore, this method can be applied to three-dimensional （3D） hybrid or spherical radial k-space sampling for a more efficient reduction of aliasing artifacts.     

Multi-model predictive control of Hammerstein-Wiener systems based on balanced multi-model partition

ABSTRACT

Model analysis of Hammerstein-Wiener systems has been made, and it is found that the included angle is applicable to such systems to measure the non-linearity. Then, a dichotomy gridding algorithm is proposed based on the included angle. Supporting by the gridding algorithm, a balanced multi-model partition method is put forward to partition a Hammerstein-Wiener system into a set of local linear models. For each linear model, a linear model predictive controller (MPC) is designed. After that, a multi-MPC is composed of the linear MPCs via soft switching. Thus, a complex non-linear control problem is transformed into a set of linear control problems, which simplifies the original control problem and improves the control performance. Two non-linear systems are built into Hammerstein-Wiener models and investigated using the proposed methods. Simulations demonstrate that the proposed gridding and partition methods are effective, and the resulted multi-MPC controller has satisfactory performance in both set-point tracking and disturbance rejection control.     

自导航快速自旋回波在低场MRI上的实现

低场磁共振成像仪一般需采用数据累加的办法来提高图像信噪比,这样会延长扫描时间,因此更易受运动伪影的影响. 为了解决运动伪影问题,本文在低场磁共振成像仪上实现了自导航快速自旋回波去运动伪影成像技术,并且与常规快速自旋回波序列进行了临床对比实验. 结果表明,与常规快速自旋回波序列相比,采用自导航快速自旋回波技术后,由于病人运动导致的伪影得到明显地抑制.      

DNA中编码序列的分形特征研究

随着基因组数据库的日益增大，如何从这庞大的数据库中提取有用的信息已成为全世界科学家迫在眉睫的难题。本文运用网格维数分别刻画了60个人类基因序列编码区的分形特征。研究结果表明：在同一个基因中，外显子的维数一般要大于整个蛋白质编码序列的维数，并通过对比随机序列的网格维数，证实了这一结论。结合分形理论及功率谱研究可以得出，具有较少外显子的基因，外显子中包含有较多的遗传信息，而对于较多外显子的基因则相反，遗传信息可能储存于内含子中。这些结论对内含子功能以及DNA序列的复杂性的研究具有一定的理论意义和实用价值。     

A new linogram algorithm for computerized tomography

We propose a new linogram algorithm for the high quality Fourierreconstruction of digital N x N images from their Radon transform.The algorithm is based on univariate fast Fourier transformsfor nonequispaced data in the time domain and in the frequencydomain. The algorithm requires only O(N² logN) arithmetic operationsand preserves the good reconstruction quality of the filteredbackprojection.     

混合式非致冷焦平面器件芯片工艺研究

随着红外热成像应用技术的不断发展，国内外研究和开发低成本非致冷热像仪的兴趣越来越浓。而开发非致冷热像仪的关键技术在于开发其核心部件非致冷焦平面器件。本文对致冷型焦平面器件和非致冷型焦平面器件进行简单的比较，简要报导国内外非致冷焦平面器件的发展状况、规模、目前达到的水平及其应用，着重叙述混合式１２８×１２８非致冷焦平面器件芯片的研制工艺。