A Multi‐Thresholding Algorithm for Sizing out of Focus Particles

A methodology is presented that enables efficient acquisition of sufficient droplet information (e.g. diameter and aspect ratio) from images of in and out of focus droplets. The newly developed multi‐threshold algorithm is successfully implemented in the automatic particle/droplet image analysis (PDIA) system. Under the same optical hardware set‐up, and compared to the dual threshold methods [1], the multi‐threshold method increases the measurable/acceptable depth of field (DoF) of particles, especially for the small particles of diameters less than 50 μm (1098 pixels in this optical set‐up). When testing the 70 μm~110 μm and 100 μm~200 μm moving glass spheres, the dual threshold method can only detect 11%~29 % of the particles found by the multi‐threshold method. The multi‐threshold method is also capable of generating the aspect ratios of particles more accurately than dual threshold methods.     

Planar Droplet Sizing for the Characterization of Droplet Clusters in an Industrial Gun‐Type Burner

An important problem in spray combustion deals with the existence of dense regions of droplets, called clusters. To understand their formation mechanism, the droplet dynamics and fuel concentration profile are investigated by means of planar laser techniques in an industrial gun‐type burner. The simultaneous measurement of elastic Mie scattering and Laser Induced Fluorescence (LIF) allows the instantaneous measurement of the Sauter Mean Diameter (SMD), after proper calibration. Using two different CCDs to get the two signals requires a detailed calibration of the CCD response before getting absolute diameters. Pixels are binned 6 by 6 to obtain the final SMD map, this is a compromise between spatial accuracy and noise. Velocity field is measured on both sets of images using standard Particle Image Velocimetry (PIV) algorithms. The comparison of cross‐correlation technique with PDA results shows that the velocity measured on the LIF images are close to the velocity based on D₃₀, whereas the Mie scattering results are similar to D₂₀. On Mie scattering images, regions of high interfacial area forming clusters can be detected. A special tracking scheme is used to characterize their dynamics in terms of velocity and diameters by ensuring that the same volume of fluid is tracked. It is shown that the clusters have a velocity similar to the velocity of droplets with the same diameter as the mean SMD of the cluster. It is also shown that an increase of pressure tends to trigger the appearance of such a group of droplets, due to a smaller diameter of the droplets caused by the increase of pressure discharge. Uncertainties for the different techniques used are discussed.     

Size and Shape Analysis of Sedimentary Grains by Automated Dynamic Image Analysis

The application of Automated Dynamic Image Analysis (ADIA) for measuring the size and shape of sedimentary grains is presented. This technique determines the size and shape of a large number of particles (typically 5,000 to 50,000 or greater) in the size range between 10 to 1,500 μm. ADIA measurements are carried out using a RapidVue particle analyzer. The size and shape of particles are obtained by analyzing digital images. Each image is composed of shapes representing two‐dimensional projections of particles. The analysis yields the area and perimeter of each particle cross‐section, which are transformed into size‐independent shape values. The analysis of such a large number of particles results in a very small statistical variation of the results, ca. 0.3% for 50,000 particles. Since operator selection of images does not enter the measurement procedure, the risk of bias caused by subjective sample selection is eliminated. The combination of ADIA with a two‐dimensional Kolmogorov‐Smirnov test, allows the identification of similarities and differences between sedimentary grains.     

Use of Video Enhanced Microscopy for Characterization of Solid‐Liquid‐Liquid Mixtures

Although some particle sizing devices have gained a lot of popularity, none of them is able to distinguish between drops and solids and few are able to handle viscous oily samples. This paper discusses the use of the optical microscopy, enhanced by the use of digital video capabilities and image analysis software, to characterize oil production wastes. Several thousands of particles were counted and their projected areas were measured. A discussion is given about the different corrections required in order to extract the most reliable information from the image analysis, overcoming some of the drawbacks of this kind of measurements. The technique developed here offers unique features like the determination of the fraction of droplets that exist in the form of non‐coalesced agglomerates. When cross‐linked with the results obtained by standard ASTM procedures, it allows to infer the amount of disperse phase that exists in the form of submicron droplets or large free water drops that are usually not sampled for microscope slides.     

Digital Optics: Some Remarks on the Accuracy of Particle Image Analysis

The article has the aim to investigate some typical errors which arise in digital images of particles, and where it is possible, tries to assess the effective inaccuracies in the determination of distributions of size, length, perimeter and shape. In the second chapter, the errors typical for very low pixel numbers are discussed, in the third chapter, resolution independent errors in the determination of length and perimeter are investigated. In the last chapter, the consequences for shape determination are summarised.     

基于图像处理的频域有限差分法用于实际光子晶体光纤的研究

提出了一种基于图像处理算法和频域有限差分法相结合研究实际光子晶体光纤的数值分析方法.该方法针对实际光子晶体光纤由于结构不规则难以进行数值分析的缺点.采取首先对光子品体光纤的电镜扫描图像使用阈值分割和维纳滤波等图像处理算法获得光纤截面的几何网像.然后使用图像插值及构造均值移动窗口滤波等方法实现了网格划分和介电系数平均等步骤,最后结合频域有限差分法对光纤特性进行分析计算.结果表明,该方法能够精确分析实际光子晶体光纤的色散特性.模拟得到的实际光子晶体光纤的模场分布与实验结果吻合很好.     

Ammonolysis of morpholine‐2,5‐diones: participation of the primary amide group. Part 2

The ammonolysis of three morpholine‐2,5‐dione derivatives was investigated and the mechanism ascertained by kinetic studies and theoretical calculations. The kinetics, followed by high‐performance liquid chromatography analysis, evidenced the presence of two intermediates, which were isolated and characterized. The ammonolysis occurs with a complex mechanism involving two consecutive reactions followed by two parallel ones. The second step of the whole reaction involves an anchimeric assistance of the primary amide group. The pseudo‐first‐order rate constants were calculated by appropriate equations, which describe the single steps of the process. Computational density functional theory investigations of vicinal primary amide group participation were performed using a model compound, and the transition states were generated. The theoretical calculations evidenced the essential role exerted by ammonia, which acts as a proton transfer. Copyright © 2011 John Wiley & Sons, Ltd.     

Accuracy of stress measurement by Laue microdiffraction (Laue‐DIC method): the influence of image noise,calibration errors and spot number

Laue microdiffraction, available at several synchrotron radiation facilities, is well suited for measuring the intragranular stress field in deformed materials thanks to the achievable submicrometer beam size. The traditional method for extracting elastic strain (and hence stress) and lattice orientation from a microdiffraction image relies on fitting each Laue spot with an analytical function to estimate the peak position on the detector screen. The method is thus limited to spots exhibiting ellipsoidal shapes, thereby impeding the study of specimens plastically deformed. To overcome this difficulty, the so‐called Laue‐DIC method introduces digital image correlation (DIC) for the evaluation of the relative positions of spots, which can thus be of any shape. This paper is dedicated to evaluating the accuracy of this Laue‐DIC method. First, a simple image noise model is established and verified on the data acquired at beamline BM32 of the European Synchrotron Radiation Facility. Then, the effect of image noise on errors on spot displacement measured by DIC is evaluated by Monte Carlo simulation. Finally, the combined effect of the image noise, calibration errors and the number of Laue spots used for data treatment is investigated. Results in terms of the uncertainty of stress measurement are provided, and various error regimes are identified.     

A robust method for high‐precision quantification of the complex three‐dimensional vasculatures acquired by X‐ray microtomography

The quantification of micro‐vasculatures is important for the analysis of angiogenesis on which the detection of tumor growth or hepatic fibrosis depends. Synchrotron‐based X‐ray computed micro‐tomography (SR‐µCT) allows rapid acquisition of micro‐vasculature images at micrometer‐scale spatial resolution. Through skeletonization, the statistical features of the micro‐vasculature can be extracted from the skeleton of the micro‐vasculatures. Thinning is a widely used algorithm to produce the vascular skeleton in medical research. Existing three‐dimensional thinning methods normally emphasize the preservation of topological structure rather than geometrical features in generating the skeleton of a volumetric object. This results in three problems and limits the accuracy of the quantitative results related to the geometrical structure of the vasculature. The problems include the excessively shortened length of elongated objects, eliminated branches of blood vessel tree structure, and numerous noisy spurious branches. The inaccuracy of the skeleton directly introduces errors in the quantitative analysis, especially on the parameters concerning the vascular length and the counts of vessel segments and branching points. In this paper, a robust method using a consolidated end‐point constraint for thinning, which generates geometry‐preserving skeletons in addition to maintaining the topology of the vasculature, is presented. The improved skeleton can be used to produce more accurate quantitative results. Experimental results from high‐resolution SR‐µCT images show that the end‐point constraint produced by the proposed method can significantly improve the accuracy of the skeleton obtained using the existing ITK three‐dimensional thinning filter. The produced skeleton has laid the groundwork for accurate quantification of the angiogenesis. This is critical for the early detection of tumors and assessing anti‐angiogenesis treatments.