A moving grid finite element method applied to a model biological pattern generator

Many problems in biology involve growth. In numerical simulations it can therefore be very convenient to employ a moving computational grid on a continuously deforming domain. In this paper we present a novel application of the moving grid finite element method to compute solutions of reaction–diffusion systems in two-dimensional continuously deforming Euclidean domains. A numerical software package has been developed as a result of this research that is capable of solving generalised Turing models for morphogenesis.     

时频域分形维数分析的光谱信号重叠峰解析算法

由于光谱谱线存在自然展宽、多普勒展宽、碰撞展宽等,使混合气体中多种成分的吸收光谱信号出现相邻谱峰重叠现象,给混合气体组成成分的定性或定量检测带来较大的困难。现有的方法在获取先验知识、处理精度、运算效率等方面存在不足。提出基于时频域分形维数分析的光谱信号重叠峰解析算法,结合小波的多尺度观测能力和分形的自相似度的度量能力,识别、定位和解析光谱信号中的重叠峰。首先利用小波对具有重叠谱峰的光谱信号进行光谱频率域和尺度域的分析,然后对该时频域的光谱信号在同一光谱频率下的多尺度数据进行自相似性度量和分形计算。逐频率计算后得到光谱信号在频率域的分形维数曲线。该曲线体现了光谱信号在不同尺度的自相似性,其极值位置与光谱信号的各独立峰的位置具有相关性。依据此特性,结合分形曲线的特征参数,最后利用神经网络解析出对应混合气体成分的混叠在一起的各个独立谱峰。该方法利用小波的多分辨率特性,对信号进行不同尺度的精细度量。分形模型则提高了系统解析复杂信号的能力,对重叠程度高的多谱峰重叠信号也有很强的处理能力。借助人工神经网络,实现了整个算法的自动测量。通过实验结果分析,验证了算法的有效性,并讨论影响算法效果的主要因素。     

Recognition and elimination of diversified pathogens in insect defense systems

Summary The elimination of infectious non-self by the host defense systems of multicellular organisms requires a variety of recognition and effector molecules. The diversity is generated in somatic cells or encoded in the germ-line. In adaptive immunity in jawed vertebrates, the diversity of immunoglobulins and antigen receptors is generated by gene rearrangements in somatic cells. In innate immunity, various effector molecules and pattern recognition receptors, such as antimicrobial peptides and peptidoglycan recognition proteins, are encoded in the germ-line of multicellular organisms, including insects and jawed vertebrates. In the present review, we discuss how insect host defense systems recognize and eliminate a multitude of microbes via germ-line-encoded molecules, including recent findings that a Drosophila member of the immunoglobulin superfamily is extensively diversified by alternative splicing in somatic immune cells and participates in the elimination of bacteria.     

Interferometric monitoring of single-mode operation of a tunable injection laser

We propose a technique for rapid monitoring of single-mode operation of a tunable injection laser, based on analysis of the fine structure of the power-current characteristic obtained with self-heterodyning, using a Michelson interferometer. The technique makes it possible to determine the range for single-mode lasing and mode tuning as well as the presence of spurious optical feedback, and to estimate the coherence length. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 1, pp. 119–123, January–February, 2006.     

Self-organized dot patterns on Si surfaces during noble gas ion beam erosion

The erosion of target materials with energetic ions can lead to the formation of patterns on the surface. During low-energy (?2000 eV) noble gas (Ne⁺, Ar⁺, Kr⁺, Xe⁺) ion beam erosion of silicon surfaces dot patterns evolve on the surface. Dot structures form at oblique ion incidence of 75° with respect to surface normal, with simultaneous sample rotation, at room temperature. The lateral ordering of dots increases while the dot size remains constant with ion fluence, leading to very well ordered dot patterns for prolonged sputtering. Depending on ion beam parameters, dot nanostructures have a mean size from 25 nm up to 50 nm, and a mean height up to 15 nm. The formation of dot patterns depends on the ion/target mass ratio and on the ion energy. The temporal evolution and the lateral ordering of these nanostructures is studied using scanning force microscopy (AFM).     

时间序列散斑干涉技术研究及应用

当用相干激光照射在一个连续位移或变形的漫射物体表面时,在与参考光形成干涉的接收面上即产生一随时间变化的散斑干涉场通过对这一干涉场的时间域进行分析,可实现时变位移场的定量检测本文介绍了基本时间序列散斑干涉场的扫描相位方法和时间序列相位法的相位函数解调原理,探讨了它们的计量特性,并将其用于火箭固体燃料性能的检测.     

基于统计滤波的单幅散斑条纹图的相位恢复技术

基于统计信号处理技术的贝叶斯（Bayes）估计原理，提出一种新的滤波方法。该方法能有效减少散斑条纹图中的噪声，而且仅用一幅散区斑条纹图就能获得准确的条纹相位分布，通过实例说明了该方法的处理过程。     

改进形态学相关算法以识别高相似度灰度图像

从形态学角度定义了灰度联合图像相似度，提出两种基于位表示法形态学相关算法的改进算法，通过提取位表示法的图像片边缘特征或二元化位表示法的图像片功率谱，以提高位表示法形态学相关算法对高相似度灰度图像的识别能力。     

Using multi-exposure of color fringes to measure the beating motion of a moth

A multi-exposure of color fringes method has been developed to improve the capture speed of a conventional color CCD camera. In the method, four groups of projected fringe patterns encoded with different colors and different directions are stored in one CCD frame. Therefore the capture frequency of the conventional CCD can be improved to 200 Hz. It is available to measure the insect wings with low beating frequency, such as dragonfly, moth, or butterfly, whose beating frequency is about 30–40 Hz. We have used the method to measure the beating motion of a moth successfully.     

A two-frame approach for scene-based nonuniformity correction in array sensors

This paper introduces a new scene-based technique to correct the fixed-pattern noise (FPN) in array sensors. This method registers a pair of image frames exhibiting small relative scene translation and then the noise pattern can be reconstructed using the constrained least-squares estimation. The key advantage of this technique is that the accurate estimates of the bias nonuniformity can be obtained with only two images, without imposing any assumptions on the structure of the FPN. Besides, the method works on almost static scene, and therefore does not require larger scale global motion and statistical assumptions on the scene irradiance. We test our method on synthetically generated FPN as well as with real infrared data, and experimental results demonstrate the significant reduction in FPN, validating the effectiveness of our approach. Finally, we validate the feasibility and validity of using the proposed method as a first step fostering the success of more sophisticated registration-based time-evolving correction algorithms.