Robust rigid registration of retinal angiograms through optimization

Retinal fundus photographs are employed as standard diagnostic tools in ophthalmology. Serial photographs of the flow of fluorescein and indocyanine green (ICG) dye are used to determine the areas of the retinal lesions. For objective measurements of features, the registration of the images is a necessity. In this paper, we employ optimization techniques for registration with the help of 2-parameter translational motion model of retinal angiograms, based on non-linear pre-processing (Wiener filtering and morphological gradient) and computation of the similarity criteria for the alignment of the two gradient images for any given rigid transformation. The optimization methods are effectively employed to minimize the similarity criterion.

The presence of noise, the variations in the background and the temporal variation of the fluorescence level pose serious problems in obtaining a robust registration of the retinal images. Moreover, local search strategies are not robust in the case of ICG angiograms, even if one uses a multiresolution approach.

The present work makes a systematic comparison of different optimization techniques, namely the minimization method derived from the optical flow formulation, the Nelder-Mead local search and the HCIAC ant colony metaheuristic, each optimizing a similarity criterion for the gradient images. The impact of the resolution and median filtering of gradient image is studied and the robustness of the approaches is tested through experimental studies, performed on macular fluorescein and ICG angiographies.

Our proposed optimization techniques have shown interesting results especially for high resolution difficult registration problems. Moreover, this approach seems promising for affine (6-parameter motion model) or elastical registrations.     

Global bifurcation structure of chaotic neural networks and its application to traveling salesman problems

This paper studies global bifurcation structure of the chaotic neural networks applied to solve the traveling salesman problem (TSP). The bifurcation analysis clarifies the dynamical basis of the chaotic neuro-dynamics which itinerates a variety of network states associated with possible solutions of TSP and efficiently ‘searches’ for the optimum or near-optimum solutions. By following the detailed merging process of chaotic attractors via crises, we find that the crisis-induced intermittent switches among the ruins of the previous localized chaotic attractors underly the ‘chaotic search’ for TSP solutions. On the basis of the present study, efficiency of the ‘chaotic search’ to optimization problems is discussed and a guideline is provided for tuning the bifurcation parameter value which gives rise to efficient ‘chaotic search’.     

Search for coloured objects in natural surroundings by people with abnormal colour vision

Background: People with abnormal colour vision often report difficulty seeing coloured berries and flowers in foliage, which suggests they will have a diminished capacity for visual search when target objects are marked out by colour. There is very little experimental evidence of the effect of abnormal colour vision on visual search and none relating to search for objects in natural foliage. Method: We showed 79 subjects with abnormal colour vision (seven protanopes, 10 deuteranopes, 16 protanomals and 46 deuteranomals) and 20 subjects with normal colour vision photographs of natural scenes and asked them to locate clumps of red berries, to trace the length of a red string on grass and to name the season depicted in a photograph taken in the Autumn and the same scene photographed in the Summer. Colour vision was assessed using the Ishihara, the Medmont C100, the Farnsworth D15, the Richmond HRR and the Nagel anomaloscope. Results: All the subjects with abnormal colour vision located fewer clumps of red berries than those with normal colour vision. The subjects who failed the Farnsworth D15 performed significantly worse than those who passed but the distribution of scores in the two groups overlaps. The majority of subjects with abnormal colour vision could not trace the full length of the string: only 38 per cent of anomalous trichromats who passed the Farnsworth D15 test and three per cent of those who failed it were able to trace the full length of the string. Fifty‐five per cent of those classed as having a mild deficiency by the HRR test could trace the whole string. Most dichromats were unable to identify the Autumn season and those who did may have been assisted by guessing. Most (94 per cent) of those who passed the Farnsworth D15 test and all those classified as having a ‘mild’ deficiency by the HRR test could identify the season. Conclusions: All people with abnormal colour vision, even those with a very mild deficiency, have some degree of impairment of their ability to see coloured objects in natural surroundings. A pass at the Farnsworth D15 test or a ‘mild’ classification with the Richmond HRR test identifies those likely to have the least problems with visual search and identification tasks. The results have practical implications for the selection of personnel in occupations that involve visual search in natural terrain.     

二维视觉搜索的计算机模拟

视觉搜索的模拟算法考虑两个交互作用的过程:覆盖过程(“看”)和视觉过程(“看见”)。搜索场景包含有靶,假目标和背景噪声;一个视力角模型按一定的搜索策略去覆盖场景。对模拟程序的输入是场景和靶的空间大小,随机分布的靶和假目标的数目。靶探测几率和识别几率均为物体在场景中对比度和物体离视力角中心的距离的函数。本模拟程序的目的是比较系统搜索和随机搜索的性能,验证关于计算最佳视窗宽度的公式,进而鉴别影响靶探测和识别能力的覆盖过程和视觉过程的参数,阐明它们之间的相互作用。     

大学生就业效能量表的编制

目的编制适用于我国大学生的就业的效能量表。方法在深入访谈和文献综述的基础上，编制出大学生就业效能量表，运用探索性和验证性因素分析技术对568名全日制在校本科生的就业效能的内在结构进行了探讨。结果大学生就业效能主要有3个因素组成：个性自我了解、就业信息与技能和就业应对信心，问卷的各项测量指标良好。结论本问卷可以作为测量大学生就业效能的工具。     

基于Internet的生物信息资源快速查找与利用

生物信息学是现代生命科学与信息科学、计算机科学、数学、统计学、物理学、化学等学科相互渗透而高度交叉形成的一门新兴前沿学科.生命科学的所有信息均可由计算机和因特网来进行储存、分析和传输.因特网为我们提供了大量的有关生物信息相关的数据、工具、文献、软件等资源.本文根据笔者的实践经验,对因特网上生物信息资源进行了整理和分类,总结了因特网上获取生物信息资源的途径及其利用,介绍了一些快速查找方法与技巧,以便读者更迅速更准确利用因特网上生物信息资源.     

液体姿控火箭发动机地面试验热结构分析

本文以液膜冷却结合辐射冷却的液体姿控火箭发动机为研究对象。采用一体化计算模型分析传热,同时应用有限元方法对在给定温度条件的热结构进行了耦合分析,最后讨论了推力室在外压作用及温度载荷条件下结构的屈曲稳定性。计算结果与参考的试验结果接近,最高温度误差为3.67%,说明该一体化计算传热模型的有效性。考虑热载荷作用得到的屈曲载荷值较不考虑其提高了大约5.79%。该结果为工程设计提供了有益的参考。     

Thermostructural Numerical Analysis of the Thrust Chamber of a Liquid Propellant Rocket Engine

The numerical simulation of rocket engine thrust chambers is very challenging as several damaging phenomena, such as plasticity, low-cycle-fatigue (LCF) and creep occur during its service life. The possibility of simulating the thermostructural behavior of the engine, by means of non-linear finite element analyses, allows the engineers to guarantee the structural safety of the structure. This document reports the numerical simulations developed with the aim of predicting the thermostructural behaviour and the service life of the thrust chamber of a liquid-propellant rocket engine. The work represents a step ahead of previous researches by the authors, with particular reference to the addition of the Smith-Watson-Topper (SWT) fatigue criterion, and to the implementation of a sub-modelling technique, for a more accurate assessment of the most critical section of the component. It was found that the equivalent plastic strains in the most critical nodes obtained through the sub-modelling technique were about 20% lower than those calculated without sub-modelling. Consistently with experimental tests from literature conducted on similar geometries, the most critical areas resulted to be on the internal surface of the chamber. The analyses demonstrated that the LCF damaging contribution was significant, with a life prediction for the thrust chamber of about 3400 cycles.     

柴油机发电厂对大气环境影响的调查与分析

通过对柴油机发电厂周围大气环境中污染物ＳＯ_２、ＮＯ_ｘ、ＴＳＰ、Ｂ（ａ）Ｐ、Ｐｂ的调查，表明受电厂排污影响，使调查区域出现一个高浓度大气污染带，污染物的时空变化有一定规律。因子分析结果表明主要污染物因子以ＳＯ_２和Ｂ（ａ）Ｐ为代表，尤以Ｂ（ａ）Ｐ污染为突出，应在区域污染防治中加以重视。     

一种用于噪声估计的改进最小值搜索方法

含噪语音短时功率谱的最小值搜索是噪声估计的基础。为了提高非平稳噪声估计的准确性,减小噪声水平上升时的噪声估计延时,提出了一种同时使用大、小两个搜索窗进行并行搜索的方法,最小值搜索的最终结果由两个并行搜索结果和基于噪声分类的语音存在二值判决共同决定。实验结果表明：对于高度非平稳的噪声,该方法能够有效地减小噪声估计的延时问题,显著提高增强后语音的质量。